refactor null safety migration

example/main.dart

@@ -1,18 +1,22 @@
-import 'package:http/http.dart' as http;
+import 'dart:io';
+
+import 'package:http/io_client.dart';
 import 'package:webfeed/webfeed.dart';
 
 void main() async {
-  var client = http.Client();
+  final client = IOClient(HttpClient()
+    ..badCertificateCallback =
+        ((X509Certificate cert, String host, int port) => true));
 
   // RSS feed
   var response = await client.get(
-      Uri(path: 'https://developer.apple.com/news/releases/rss/releases.rss'));
+      Uri.parse('https://developer.apple.com/news/releases/rss/releases.rss'));
   var channel = RssFeed.parse(response.body);
   print(channel);
 
   // Atom feed
   response =
-      await client.get(Uri(path: 'https://www.theverge.com/rss/index.xml'));
+      await client.get(Uri.parse('https://www.theverge.com/rss/index.xml'));
   var feed = AtomFeed.parse(response.body);
   print(feed);
 

lib/domain/atom_feed.dart

@@ -4,7 +4,7 @@ import 'package:webfeed/domain/atom_item.dart';
 import 'package:webfeed/domain/atom_link.dart';
 import 'package:webfeed/domain/atom_person.dart';
 import 'package:webfeed/util/datetime.dart';
-import 'package:webfeed/util/xml.dart';
+import 'package:webfeed/util/iterable.dart';
 import 'package:xml/xml.dart';
 
 class AtomFeed {
@@ -41,15 +41,16 @@ class AtomFeed {
 
   factory AtomFeed.parse(String xmlString) {
     var document = XmlDocument.parse(xmlString);
-    var feedElement = findFirstElement(document, 'feed');
+    var feedElement = document.findElements('feed').firstOrNull;
     if (feedElement == null) {
       throw ArgumentError('feed not found');
     }
 
     return AtomFeed(
-      id: findFirstElement(feedElement, 'id')?.text,
-      title: findFirstElement(feedElement, 'title')?.text,
-      updated: parseDateTime(findFirstElement(feedElement, 'updated')?.text),
+      id: feedElement.findElements('id').firstOrNull?.text,
+      title: feedElement.findElements('title').firstOrNull?.text,
+      updated:
+          parseDateTime(feedElement.findElements('updated').firstOrNull?.text),
       items: feedElement
           .findElements('entry')
           .map((e) => AtomItem.parse(e))
@@ -70,12 +71,14 @@ class AtomFeed {
           .findElements('category')
           .map((e) => AtomCategory.parse(e))
           .toList(),
-      generator:
-          AtomGenerator.parse(findFirstElement(feedElement, 'generator')),
-      icon: findFirstElement(feedElement, 'icon')?.text,
-      logo: findFirstElement(feedElement, 'logo')?.text,
-      rights: findFirstElement(feedElement, 'rights')?.text,
-      subtitle: findFirstElement(feedElement, 'subtitle')?.text,
+      generator: feedElement
+          .findElements('generator')
+          .map((e) => AtomGenerator.parse(e))
+          .firstOrNull,
+      icon: feedElement.findElements('icon').firstOrNull?.text,
+      logo: feedElement.findElements('logo').firstOrNull?.text,
+      rights: feedElement.findElements('rights').firstOrNull?.text,
+      subtitle: feedElement.findElements('subtitle').firstOrNull?.text,
     );
   }
 }

lib/domain/atom_generator.dart

@@ -7,8 +7,7 @@ class AtomGenerator {
 
   AtomGenerator(this.uri, this.version, this.value);
 
-  static parse(XmlElement? element) {
-    if (element == null) return null;
+  factory AtomGenerator.parse(XmlElement element) {
     var uri = element.getAttribute('uri');
     var version = element.getAttribute('version');
     var value = element.text;

lib/domain/atom_item.dart

@@ -4,7 +4,7 @@ import 'package:webfeed/domain/atom_person.dart';
 import 'package:webfeed/domain/atom_source.dart';
 import 'package:webfeed/domain/media/media.dart';
 import 'package:webfeed/util/datetime.dart';
-import 'package:webfeed/util/xml.dart';
+import 'package:webfeed/util/iterable.dart';
 import 'package:xml/xml.dart';
 
 class AtomItem {
@@ -41,9 +41,9 @@ class AtomItem {
 
   factory AtomItem.parse(XmlElement element) {
     return AtomItem(
-      id: findFirstElement(element, 'id')?.text,
-      title: findFirstElement(element, 'title')?.text,
-      updated: parseDateTime(findFirstElement(element, 'updated')?.text),
+      id: element.findElements('id').firstOrNull?.text,
+      title: element.findElements('title').firstOrNull?.text,
+      updated: parseDateTime(element.findElements('updated').firstOrNull?.text),
       authors: element
           .findElements('author')
           .map((e) => AtomPerson.parse(e))
@@ -58,11 +58,14 @@ class AtomItem {
           .findElements('contributor')
           .map((e) => AtomPerson.parse(e))
           .toList(),
-      source: AtomSource.parse(findFirstElement(element, 'source')),
-      published: findFirstElement(element, 'published')?.text,
-      content: findFirstElement(element, 'content')?.text,
-      summary: findFirstElement(element, 'summary')?.text,
-      rights: findFirstElement(element, 'rights')?.text,
+      source: element
+          .findElements('source')
+          .map((e) => AtomSource.parse(e))
+          .firstOrNull,
+      published: element.findElements('published').firstOrNull?.text,
+      content: element.findElements('content').firstOrNull?.text,
+      summary: element.findElements('summary').firstOrNull?.text,
+      rights: element.findElements('rights').firstOrNull?.text,
       media: Media.parse(element),
     );
   }

lib/domain/atom_person.dart

@@ -1,4 +1,4 @@
-import 'package:webfeed/util/xml.dart';
+import 'package:webfeed/util/iterable.dart';
 import 'package:xml/xml.dart';
 
 class AtomPerson {
@@ -10,9 +10,9 @@ class AtomPerson {
 
   factory AtomPerson.parse(XmlElement element) {
     return AtomPerson(
-      name: findFirstElement(element, 'name')?.text,
-      uri: findFirstElement(element, 'uri')?.text,
-      email: findFirstElement(element, 'email')?.text,
+      name: element.findElements('name').firstOrNull?.text,
+      uri: element.findElements('uri').firstOrNull?.text,
+      email: element.findElements('email').firstOrNull?.text,
     );
   }
 }

lib/domain/atom_source.dart

@@ -1,4 +1,4 @@
-import 'package:webfeed/util/xml.dart';
+import 'package:webfeed/util/iterable.dart';
 import 'package:xml/xml.dart';
 
 class AtomSource {
@@ -12,12 +12,11 @@ class AtomSource {
     this.updated,
   });
 
-  static parse(XmlElement? element) {
-    if (element == null) return null;
+  factory AtomSource.parse(XmlElement element) {
     return AtomSource(
-      id: findFirstElement(element, 'id')?.text,
-      title: findFirstElement(element, 'title')?.text,
-      updated: findFirstElement(element, 'updated')?.text,
+      id: element.findElements('id').firstOrNull?.text,
+      title: element.findElements('title').firstOrNull?.text,
+      updated: element.findElements('updated').firstOrNull?.text,
     );
   }
 }

lib/domain/dublin_core/dublin_core.dart

@@ -1,5 +1,5 @@
 import 'package:webfeed/util/datetime.dart';
-import 'package:webfeed/util/xml.dart';
+import 'package:webfeed/util/iterable.dart';
 import 'package:xml/xml.dart';
 
 class DublinCore {
@@ -41,28 +41,27 @@ class DublinCore {
     this.rights,
   });
 
-  static parse(XmlElement? element) {
-    if (element == null) {
-      return null;
-    }
+  factory DublinCore.parse(XmlElement element) {
     return DublinCore(
-      title: findFirstElement(element, 'dc:title')?.text,
-      description: findFirstElement(element, 'dc:description')?.text,
-      creator: findFirstElement(element, 'dc:creator')?.text,
-      subject: findFirstElement(element, 'dc:subject')?.text,
-      publisher: findFirstElement(element, 'dc:publisher')?.text,
-      contributor: findFirstElement(element, 'dc:contributor')?.text,
-      date: parseDateTime(findFirstElement(element, 'dc:date')?.text),
-      created: parseDateTime(findFirstElement(element, 'dc:created')?.text),
-      modified: parseDateTime(findFirstElement(element, 'dc:modified')?.text),
-      type: findFirstElement(element, 'dc:type')?.text,
-      format: findFirstElement(element, 'dc:format')?.text,
-      identifier: findFirstElement(element, 'dc:identifier')?.text,
-      source: findFirstElement(element, 'dc:source')?.text,
-      language: findFirstElement(element, 'dc:language')?.text,
-      relation: findFirstElement(element, 'dc:relation')?.text,
-      coverage: findFirstElement(element, 'dc:coverage')?.text,
-      rights: findFirstElement(element, 'dc:rights')?.text,
+      title: element.findElements('dc:title').firstOrNull?.text,
+      description: element.findElements('dc:description').firstOrNull?.text,
+      creator: element.findElements('dc:creator').firstOrNull?.text,
+      subject: element.findElements('dc:subject').firstOrNull?.text,
+      publisher: element.findElements('dc:publisher').firstOrNull?.text,
+      contributor: element.findElements('dc:contributor').firstOrNull?.text,
+      date: parseDateTime(element.findElements('dc:date').firstOrNull?.text),
+      created:
+          parseDateTime(element.findElements('dc:created').firstOrNull?.text),
+      modified:
+          parseDateTime(element.findElements('dc:modified').firstOrNull?.text),
+      type: element.findElements('dc:type').firstOrNull?.text,
+      format: element.findElements('dc:format').firstOrNull?.text,
+      identifier: element.findElements('dc:identifier').firstOrNull?.text,
+      source: element.findElements('dc:source').firstOrNull?.text,
+      language: element.findElements('dc:language').firstOrNull?.text,
+      relation: element.findElements('dc:relation').firstOrNull?.text,
+      coverage: element.findElements('dc:coverage').firstOrNull?.text,
+      rights: element.findElements('dc:rights').firstOrNull?.text,
     );
   }
 }

lib/domain/itunes/itunes.dart

@@ -3,6 +3,7 @@ import 'package:webfeed/domain/itunes/itunes_episode_type.dart';
 import 'package:webfeed/domain/itunes/itunes_image.dart';
 import 'package:webfeed/domain/itunes/itunes_owner.dart';
 import 'package:webfeed/domain/itunes/itunes_type.dart';
+import 'package:webfeed/util/iterable.dart';
 import 'package:webfeed/util/xml.dart';
 import 'package:xml/xml.dart';
 
@@ -15,7 +16,7 @@ class Itunes {
   final ItunesOwner? owner;
   final List<String>? keywords;
   final ItunesImage? image;
-  final List<ItunesCategory?>? categories;
+  final List<ItunesCategory>? categories;
   final ItunesType? type;
   final String? newFeedUrl;
   final bool? block;
@@ -45,39 +46,51 @@ class Itunes {
     this.episodeType,
   });
 
-  static parse(XmlElement? element) {
-    if (element == null) {
-      return null;
-    }
-    var episodeStr = findFirstElement(element, 'itunes:episode')?.text;
-    var seasonStr = findFirstElement(element, 'itunes:season')?.text;
-    var durationStr = findFirstElement(element, 'itunes:duration')?.text;
+  factory Itunes.parse(XmlElement element) {
+    final episodeStr = element.findElements('itunes:episode').firstOrNull?.text;
+    final seasonStr = element.findElements('itunes:season').firstOrNull?.text;
+    final durationStr =
+        element.findElements('itunes:duration').firstOrNull?.text;
     return Itunes(
-      author: findFirstElement(element, 'itunes:author')?.text,
-      summary: findFirstElement(element, 'itunes:summary')?.text,
+      author: element.findElements('itunes:author').firstOrNull?.text,
+      summary: element.findElements('itunes:summary').firstOrNull?.text,
       explicit: parseBoolLiteral(element, 'itunes:explicit'),
-      title: findFirstElement(element, 'itunes:title')?.text,
-      subtitle: findFirstElement(element, 'itunes:subtitle')?.text,
-      owner: ItunesOwner.parse(findFirstElement(element, 'itunes:owner')),
-      keywords: findFirstElement(element, 'itunes:keywords')
+      title: element.findElements('itunes:title').firstOrNull?.text,
+      subtitle: element.findElements('itunes:subtitle').firstOrNull?.text,
+      owner: element
+          .findElements('itunes:owner')
+          .map((e) => ItunesOwner.parse(e))
+          .firstOrNull,
+      keywords: element
+              .findElements('itunes:keywords')
+              .firstOrNull
               ?.text
               .split(',')
               .map((keyword) => keyword.trim())
               .toList() ??
           [],
-      image: ItunesImage.parse(findFirstElement(element, 'itunes:image')),
-      categories: findElements(element, 'itunes:category')!
+      image: element
+          .findElements('itunes:image')
+          .map((e) => ItunesImage.parse(e))
+          .firstOrNull,
+      categories: element
+          .findElements('itunes:category')
           .map((e) => ItunesCategory.parse(e))
           .toList(),
-      type: newItunesType(findFirstElement(element, 'itunes:type')),
-      newFeedUrl: findFirstElement(element, 'itunes:new-feed-url')?.text,
+      type: element
+          .findElements('itunes:type')
+          .map((e) => newItunesType(e))
+          .firstOrNull,
+      newFeedUrl: element.findElements('itunes:new-feed-url').firstOrNull?.text,
       block: parseBoolLiteral(element, 'itunes:block'),
       complete: parseBoolLiteral(element, 'itunes:complete'),
-      episode: episodeStr == null ? null : int.parse(episodeStr),
-      season: seasonStr == null ? null : int.parse(seasonStr),
+      episode: episodeStr == null ? null : int.tryParse(episodeStr),
+      season: seasonStr == null ? null : int.tryParse(seasonStr),
       duration: durationStr == null ? null : _parseDuration(durationStr),
-      episodeType:
-          newItunesEpisodeType(findFirstElement(element, 'itunes:episodeType')),
+      episodeType: element
+          .findElements('itunes:episodeType')
+          .map((e) => newItunesEpisodeType(e))
+          .firstOrNull,
     );
   }
 
@@ -87,12 +100,12 @@ class Itunes {
     var seconds = 0;
     var parts = s.split(':');
     if (parts.length > 2) {
-      hours = int.parse(parts[parts.length - 3]);
+      hours = int.tryParse(parts[parts.length - 3]) ?? 0;
     }
     if (parts.length > 1) {
-      minutes = int.parse(parts[parts.length - 2]);
+      minutes = int.tryParse(parts[parts.length - 2]) ?? 0;
     }
-    seconds = int.parse(parts[parts.length - 1]);
+    seconds = int.tryParse(parts[parts.length - 1]) ?? 0;
     return Duration(
       hours: hours,
       minutes: minutes,

lib/domain/itunes/itunes_category.dart

@@ -2,17 +2,16 @@ import 'package:xml/xml.dart';
 
 class ItunesCategory {
   final String? category;
-  final List<String?>? subCategories;
+  final List<String>? subCategories;
 
   ItunesCategory({this.category, this.subCategories});
 
-  static ItunesCategory? parse(XmlElement? element) {
-    if (element == null) return null;
+  factory ItunesCategory.parse(XmlElement element) {
     return ItunesCategory(
         category: element.getAttribute('text')?.trim(),
         subCategories: element
             .findElements('itunes:category')
-            .map((e) => e.getAttribute('text')?.trim())
+            .map((e) => e.getAttribute('text')?.trim() ?? '')
             .toList());
   }
 }

lib/domain/itunes/itunes_episode_type.dart

@@ -2,8 +2,8 @@ import 'package:xml/xml.dart';
 
 enum ItunesEpisodeType { full, trailer, bonus, unknown }
 
-ItunesEpisodeType newItunesEpisodeType(XmlElement? element) {
-  switch (element?.text) {
+ItunesEpisodeType newItunesEpisodeType(XmlElement element) {
+  switch (element.text) {
     case 'full':
       return ItunesEpisodeType.full;
     case 'trailer':

lib/domain/itunes/itunes_image.dart

@@ -5,13 +5,9 @@ class ItunesImage {
 
   ItunesImage({this.href});
 
-  static parse(XmlElement? element) {
-    ItunesImage? result;
-    if (element == null) return null;
-    result = ItunesImage(
+  factory ItunesImage.parse(XmlElement element) {
+    return ItunesImage(
       href: element.getAttribute('href')?.trim(),
     );
-
-    return result;
   }
 }

lib/domain/itunes/itunes_owner.dart

@@ -1,4 +1,4 @@
-import 'package:webfeed/util/xml.dart';
+import 'package:webfeed/util/iterable.dart';
 import 'package:xml/xml.dart';
 
 class ItunesOwner {
@@ -7,10 +7,10 @@ class ItunesOwner {
 
   ItunesOwner({this.name, this.email});
 
-  factory ItunesOwner.parse(XmlElement? element) {
+  factory ItunesOwner.parse(XmlElement element) {
     return ItunesOwner(
-      name: findFirstElement(element, 'itunes:name')?.text.trim(),
-      email: findFirstElement(element, 'itunes:email')?.text.trim(),
+      name: element.findElements('itunes:name').firstOrNull?.text.trim(),
+      email: element.findElements('itunes:email').firstOrNull?.text.trim(),
     );
   }
 }

lib/domain/itunes/itunes_type.dart

@@ -2,8 +2,8 @@ import 'package:xml/xml.dart';
 
 enum ItunesType { episodic, serial, unknown }
 
-ItunesType newItunesType(XmlElement? element) {
-  switch (element?.text) {
+ItunesType newItunesType(XmlElement element) {
+  switch (element.text) {
     case 'episodic':
       return ItunesType.episodic;
     case 'serial':

lib/domain/media/category.dart

@@ -11,8 +11,7 @@ class Category {
     this.value,
   });
 
-  static parse(XmlElement? element) {
-    if (element == null) return null;
+  factory Category.parse(XmlElement element) {
     return Category(
       scheme: element.getAttribute('scheme'),
       label: element.getAttribute('label'),

lib/domain/media/community.dart

@@ -1,7 +1,7 @@
 import 'package:webfeed/domain/media/star_rating.dart';
 import 'package:webfeed/domain/media/statistics.dart';
 import 'package:webfeed/domain/media/tags.dart';
-import 'package:webfeed/util/xml.dart';
+import 'package:webfeed/util/iterable.dart';
 import 'package:xml/xml.dart';
 
 class Community {
@@ -15,18 +15,20 @@ class Community {
     this.tags,
   });
 
-  static parse(XmlElement? element) {
-    if (element == null) return null;
+  factory Community.parse(XmlElement element) {
     return Community(
-      starRating: StarRating.parse(
-        findFirstElement(element, 'media:starRating'),
-      ),
-      statistics: Statistics.parse(
-        findFirstElement(element, 'media:statistics'),
-      ),
-      tags: Tags.parse(
-        findFirstElement(element, 'media:tags'),
-      ),
+      starRating: element
+          .findElements('media:starRating')
+          .map((e) => StarRating.parse(e))
+          .firstOrNull,
+      statistics: element
+          .findElements('media:statistics')
+          .map((e) => Statistics.parse(e))
+          .firstOrNull,
+      tags: element
+          .findElements('media:tags')
+          .map((e) => Tags.parse(e))
+          .firstOrNull,
     );
   }
 }

lib/domain/media/copyright.dart

@@ -9,8 +9,7 @@ class Copyright {
     this.value,
   });
 
-  static parse(XmlElement? element) {
-    if (element == null) return null;
+  factory Copyright.parse(XmlElement element) {
     return Copyright(
       url: element.getAttribute('url'),
       value: element.text,

lib/domain/media/description.dart

@@ -9,8 +9,7 @@ class Description {
     this.value,
   });
 
-  static parse(XmlElement? element) {
-    if (element == null) return null;
+  factory Description.parse(XmlElement element) {
     return Description(
       type: element.getAttribute('type'),
       value: element.text,

lib/domain/media/embed.dart

@@ -5,7 +5,7 @@ class Embed {
   final String? url;
   final int? width;
   final int? height;
-  final List<Param?>? params;
+  final List<Param>? params;
 
   Embed({
     this.url,
@@ -14,15 +14,15 @@ class Embed {
     this.params,
   });
 
-  static parse(XmlElement? element) {
-    if (element == null) return null;
+  factory Embed.parse(XmlElement element) {
     return Embed(
       url: element.getAttribute('url'),
       width: int.tryParse(element.getAttribute('width') ?? '0'),
       height: int.tryParse(element.getAttribute('height') ?? '0'),
-      params: element.findElements('media:param').map((e) {
-        return Param.parse(e);
-      }).toList(),
+      params: element
+          .findElements('media:param')
+          .map((e) => Param.parse(e))
+          .toList(),
     );
   }
 }

lib/domain/media/group.dart

@@ -2,7 +2,7 @@ import 'package:webfeed/domain/media/category.dart';
 import 'package:webfeed/domain/media/content.dart';
 import 'package:webfeed/domain/media/credit.dart';
 import 'package:webfeed/domain/media/rating.dart';
-import 'package:webfeed/util/xml.dart';
+import 'package:webfeed/util/iterable.dart';
 import 'package:xml/xml.dart';
 
 class Group {
@@ -18,21 +18,24 @@ class Group {
     this.rating,
   });
 
-  static parse(XmlElement? element) {
-    if (element == null) return null;
+  factory Group.parse(XmlElement element) {
     return Group(
-      contents: element.findElements('media:content').map((e) {
-        return Content.parse(e);
-      }).toList(),
-      credits: element.findElements('media:credit').map((e) {
-        return Credit.parse(e);
-      }).toList(),
-      category: Category.parse(
-        findFirstElement(element, 'media:category'),
-      ),
-      rating: Rating.parse(
-        findFirstElement(element, 'media:rating'),
-      ),
+      contents: element
+          .findElements('media:content')
+          .map((e) => Content.parse(e))
+          .toList(),
+      credits: element
+          .findElements('media:credit')
+          .map((e) => Credit.parse(e))
+          .toList(),
+      category: element
+          .findElements('media:category')
+          .map((e) => Category.parse(e))
+          .firstOrNull,
+      rating: element
+          .findElements('media:rating')
+          .map((e) => Rating.parse(e))
+          .firstOrNull,
     );
   }
 }

lib/domain/media/hash.dart

@@ -9,8 +9,7 @@ class Hash {
     this.value,
   });
 
-  static parse(XmlElement? element) {
-    if (element == null) return null;
+  factory Hash.parse(XmlElement element) {
     return Hash(
       algo: element.getAttribute('algo'),
       value: element.text,

lib/domain/media/license.dart

@@ -11,8 +11,7 @@ class License {
     this.value,
   });
 
-  static parse(XmlElement? element) {
-    if (element == null) return null;
+  factory License.parse(XmlElement element) {
     return License(
       type: element.getAttribute('type'),
       href: element.getAttribute('href'),

lib/domain/media/media.dart

@@ -20,6 +20,7 @@ import 'package:webfeed/domain/media/text.dart';
 import 'package:webfeed/domain/media/thumbnail.dart';
 import 'package:webfeed/domain/media/title.dart';
 import 'package:webfeed/util/xml.dart';
+import 'package:webfeed/util/iterable.dart';
 import 'package:xml/xml.dart';
 
 class Media {
@@ -47,7 +48,7 @@ class Media {
   final License? license;
   final PeerLink? peerLink;
   final Rights? rights;
-  final List<Scene?>? scenes;
+  final List<Scene>? scenes;
 
   Media({
     this.group,
@@ -79,90 +80,113 @@ class Media {
 
   factory Media.parse(XmlElement element) {
     return Media(
-      group: Group.parse(
-        findFirstElement(element, 'media:group'),
-      ),
-      contents: element.findElements('media:content').map((e) {
-        return Content.parse(e);
-      }).toList(),
-      credits: element.findElements('media:credit').map((e) {
-        return Credit.parse(e);
-      }).toList(),
-      category: Category.parse(
-        findFirstElement(element, 'media:category'),
-      ),
-      rating: Rating.parse(
-        findFirstElement(element, 'media:rating'),
-      ),
-      title: Title.parse(
-        findFirstElement(element, 'media:title'),
-      ),
-      description: Description.parse(
-        findFirstElement(element, 'media:description'),
-      ),
-      keywords: findFirstElement(element, 'media:keywords')?.text,
-      thumbnails: element.findElements('media:thumbnail').map((e) {
-        return Thumbnail.parse(e);
-      }).toList(),
-      hash: Hash.parse(
-        findFirstElement(element, 'media:hash'),
-      ),
-      player: Player.parse(
-        findFirstElement(element, 'media:player'),
-      ),
-      copyright: Copyright.parse(
-        findFirstElement(element, 'media:copyright'),
-      ),
-      text: Text.parse(
-        findFirstElement(element, 'media:text'),
-      ),
-      restriction: Restriction.parse(
-        findFirstElement(element, 'media:restriction'),
-      ),
-      community: Community.parse(
-        findFirstElement(element, 'media:community'),
-      ),
-      comments: findFirstElement(element, 'media:comments')
+      group: element
+          .findElements('media:group')
+          .map((e) => Group.parse(e))
+          .firstOrNull,
+      contents: element
+          .findElements('media:content')
+          .map((e) => Content.parse(e))
+          .toList(),
+      credits: element
+          .findElements('media:credit')
+          .map((e) => Credit.parse(e))
+          .toList(),
+      category: element
+          .findElements('media:category')
+          .map((e) => Category.parse(e))
+          .firstOrNull,
+      rating: element
+          .findElements('media:rating')
+          .map((e) => Rating.parse(e))
+          .firstOrNull,
+      title: findElements(element, 'media:title')
+          ?.map((e) => Title.parse(e))
+          .firstOrNull,
+      description: element
+          .findElements('media:description')
+          .map((e) => Description.parse(e))
+          .firstOrNull,
+      keywords: element.findElements('media:keywords').firstOrNull?.text,
+      thumbnails: element
+          .findElements('media:thumbnail')
+          .map((e) => Thumbnail.parse(e))
+          .toList(),
+      hash: element
+          .findElements('media:hash')
+          .map((e) => Hash.parse(e))
+          .firstOrNull,
+      player: element
+          .findElements('media:player')
+          .map((e) => Player.parse(e))
+          .firstOrNull,
+      copyright: element
+          .findElements('media:copyright')
+          .map((e) => Copyright.parse(e))
+          .firstOrNull,
+      text: element
+          .findElements('media:text')
+          .map((e) => Text.parse(e))
+          .firstOrNull,
+      restriction: element
+          .findElements('media:restriction')
+          .map((e) => Restriction.parse(e))
+          .firstOrNull,
+      community: element
+          .findElements('media:community')
+          .map((e) => Community.parse(e))
+          .firstOrNull,
+      comments: element
+              .findElements('media:comments')
+              .firstOrNull
               ?.findElements('media:comment')
-              .map((e) {
-            return e.text;
-          }).toList() ??
+              .map((e) => e.text)
+              .toList() ??
           [],
-      embed: Embed.parse(
-        findFirstElement(element, 'media:embed'),
-      ),
-      responses: findFirstElement(element, 'media:responses')
+      embed: element
+          .findElements('media:embed')
+          .map((e) => Embed.parse(e))
+          .firstOrNull,
+      responses: element
+              .findElements('media:responses')
+              .firstOrNull
               ?.findElements('media:response')
-              .map((e) {
-            return e.text;
-          }).toList() ??
+              .map((e) => e.text)
+              .toList() ??
           [],
-      backLinks: findFirstElement(element, 'media:backLinks')
+      backLinks: element
+              .findElements('media:backLinks')
+              .firstOrNull
               ?.findElements('media:backLink')
-              .map((e) {
-            return e.text;
-          }).toList() ??
+              .map((e) => e.text)
+              .toList() ??
           [],
-      status: Status.parse(
-        findFirstElement(element, 'media:status'),
-      ),
-      prices: element.findElements('media:price').map((e) {
-        return Price.parse(e);
-      }).toList(),
-      license: License.parse(
-        findFirstElement(element, 'media:license'),
-      ),
-      peerLink: PeerLink.parse(
-        findFirstElement(element, 'media:peerLink'),
-      ),
-      rights: Rights.parse(
-        findFirstElement(element, 'media:rights'),
-      ),
-      scenes: findFirstElement(element, 'media:scenes')
+      status: element
+          .findElements('media:status')
+          .map((e) => Status.parse(e))
+          .firstOrNull,
+      prices: element
+          .findElements('media:price')
+          .map((e) => Price.parse(e))
+          .toList(),
+      license: element
+          .findElements('media:license')
+          .map((e) => License.parse(e))
+          .firstOrNull,
+      peerLink: element
+          .findElements('media:peerLink')
+          .map((e) => PeerLink.parse(e))
+          .firstOrNull,
+      rights: element
+          .findElements('media:rights')
+          .map((e) => Rights.parse(e))
+          .firstOrNull,
+      scenes: element
+              .findElements('media:scenes')
+              .firstOrNull
               ?.findElements('media:scene')
-              .map((e) {
-            return Scene.parse(e);
-          }).toList() ??
+              .map((e) => Scene.parse(e))
+              .toList() ??
           [],
     );
   }

lib/domain/media/param.dart

@@ -9,8 +9,7 @@ class Param {
     this.value,
   });
 
-  static Param? parse(XmlElement? element) {
-    if (element == null) return null;
+  factory Param.parse(XmlElement element) {
     return Param(
       name: element.getAttribute('name'),
       value: element.text,

lib/domain/media/peer_link.dart

@@ -11,8 +11,7 @@ class PeerLink {
     this.value,
   });
 
-  static parse(XmlElement? element) {
-    if (element == null) return null;
+  factory PeerLink.parse(XmlElement element) {
     return PeerLink(
       type: element.getAttribute('type'),
       href: element.getAttribute('href'),

lib/domain/media/player.dart

@@ -13,8 +13,7 @@ class Player {
     this.value,
   });
 
-  static parse(XmlElement? element) {
-    if (element == null) return null;
+  factory Player.parse(XmlElement element) {
     return Player(
       url: element.getAttribute('url'),
       width: int.tryParse(element.getAttribute('width') ?? '0'),

lib/domain/media/rating.dart

@@ -9,8 +9,7 @@ class Rating {
     this.value,
   });
 
-  static parse(XmlElement? element) {
-    if (element == null) return null;
+  factory Rating.parse(XmlElement element) {
     return Rating(
       scheme: element.getAttribute('scheme'),
       value: element.text,

lib/domain/media/restriction.dart

@@ -11,8 +11,7 @@ class Restriction {
     this.value,
   });
 
-  static parse(XmlElement? element) {
-    if (element == null) return null;
+  factory Restriction.parse(XmlElement element) {
     return Restriction(
       relationship: element.getAttribute('relationship'),
       type: element.getAttribute('type'),

lib/domain/media/rights.dart

@@ -7,8 +7,7 @@ class Rights {
     this.status,
   });
 
-  static parse(XmlElement? element) {
-    if (element == null) return null;
+  factory Rights.parse(XmlElement element) {
     return Rights(
       status: element.getAttribute('status'),
     );

lib/domain/media/scene.dart

@@ -1,4 +1,4 @@
-import 'package:webfeed/util/xml.dart';
+import 'package:webfeed/util/iterable.dart';
 import 'package:xml/xml.dart';
 
 class Scene {
@@ -14,13 +14,12 @@ class Scene {
     this.endTime,
   });
 
-  static Scene? parse(XmlElement? element) {
-    if (element == null) return null;
+  factory Scene.parse(XmlElement element) {
     return Scene(
-      title: findFirstElement(element, 'sceneTitle')?.text,
-      description: findFirstElement(element, 'sceneDescription')?.text,
-      startTime: findFirstElement(element, 'sceneStartTime')?.text,
-      endTime: findFirstElement(element, 'sceneEndTime')?.text,
+      title: element.findElements('sceneTitle').firstOrNull?.text,
+      description: element.findElements('sceneDescription').firstOrNull?.text,
+      startTime: element.findElements('sceneStartTime').firstOrNull?.text,
+      endTime: element.findElements('sceneEndTime').firstOrNull?.text,
     );
   }
 }

lib/domain/media/status.dart

@@ -9,8 +9,7 @@ class Status {
     this.reason,
   });
 
-  static parse(XmlElement? element) {
-    if (element == null) return null;
+  factory Status.parse(XmlElement element) {
     return Status(
       state: element.getAttribute('state'),
       reason: element.getAttribute('reason'),

lib/domain/media/tags.dart

@@ -9,8 +9,7 @@ class Tags {
     this.weight,
   });
 
-  static parse(XmlElement? element) {
-    if (element == null) return null;
+  factory Tags.parse(XmlElement element) {
     return Tags(
       tags: element.text,
       weight: int.tryParse(element.getAttribute('weight') ?? '1'),

lib/domain/media/text.dart

@@ -15,8 +15,7 @@ class Text {
     this.value,
   });
 
-  static parse(XmlElement? element) {
-    if (element == null) return null;
+  factory Text.parse(XmlElement element) {
     return Text(
       type: element.getAttribute('type'),
       lang: element.getAttribute('lang'),

lib/domain/media/title.dart

@@ -9,8 +9,7 @@ class Title {
     this.value,
   });
 
-  static parse(XmlElement? element) {
-    if (element == null) return null;
+  factory Title.parse(XmlElement element) {
     return Title(
       type: element.getAttribute('type'),
       value: element.text,

lib/domain/rss_category.dart

@@ -6,8 +6,7 @@ class RssCategory {
 
   RssCategory(this.domain, this.value);
 
-  static RssCategory? parse(XmlElement? element) {
-    if (element == null) return null;
+  factory RssCategory.parse(XmlElement element) {
     var domain = element.getAttribute('domain');
     var value = element.text;
 

lib/domain/rss_cloud.dart

@@ -15,8 +15,7 @@ class RssCloud {
     this.protocol,
   );
 
-  static parse(XmlElement? node) {
-    if (node == null) return null;
+  factory RssCloud.parse(XmlElement node) {
     var domain = node.getAttribute('domain');
     var port = node.getAttribute('port');
     var path = node.getAttribute('path');

lib/domain/rss_content.dart

@@ -12,18 +12,15 @@ final _imagesRegExp = RegExp(
 ///
 class RssContent {
   String value;
-  Iterable<String?> images;
+  Iterable<String> images;
 
   RssContent(this.value, this.images);
 
-  static parse(XmlElement? element) {
-    if(element == null) {
-      return null;
-    }
+  factory RssContent.parse(XmlElement element) {
     final dynamic? content = element.text;
-    final images = <String?>[];
+    final images = <String>[];
     _imagesRegExp.allMatches(content).forEach((match) {
-      images.add(match.group(1));
+      images.add(match.group(1)!);
     });
     return RssContent(content, images);
   }

lib/domain/rss_enclosure.dart

@@ -7,8 +7,7 @@ class RssEnclosure {
 
   RssEnclosure(this.url, this.type, this.length);
 
-  static parse(XmlElement? element) {
-    if (element == null) return null;
+  factory RssEnclosure.parse(XmlElement element) {
     var url = element.getAttribute('url');
     var type = element.getAttribute('type');
     var length = int.tryParse(element.getAttribute('length') ?? '0');

lib/domain/rss_feed.dart

@@ -7,7 +7,7 @@ import 'package:webfeed/domain/rss_cloud.dart';
 import 'package:webfeed/domain/rss_image.dart';
 import 'package:webfeed/domain/rss_item.dart';
 import 'package:webfeed/domain/syndication/syndication.dart';
-import 'package:webfeed/util/xml.dart';
+import 'package:webfeed/util/iterable.dart';
 import 'package:xml/xml.dart';
 
 class RssFeed {
@@ -19,9 +19,9 @@ class RssFeed {
 
   final RssImage? image;
   final RssCloud? cloud;
-  final List<RssCategory?>? categories;
+  final List<RssCategory>? categories;
   final List<String>? skipDays;
-  final List<int?>? skipHours;
+  final List<int>? skipHours;
   final String? lastBuildDate;
   final String? language;
   final String? generator;
@@ -62,50 +62,62 @@ class RssFeed {
 
   factory RssFeed.parse(String xmlString) {
     var document = XmlDocument.parse(xmlString);
-    var rss = findFirstElement(document, 'rss');
-    var rdf = findFirstElement(document, 'rdf:RDF');
+    var rss = document.findElements('rss').firstOrNull;
+    var rdf = document.findElements('rdf:RDF').firstOrNull;
     if (rss == null && rdf == null) {
       throw ArgumentError('not a rss feed');
     }
-    var channelElement = findFirstElement(rss ?? rdf, 'channel');
+    var channelElement = (rss ?? rdf)!.findElements('channel').firstOrNull;
     if (channelElement == null) {
       throw ArgumentError('channel not found');
     }
     return RssFeed(
-      title: findFirstElement(channelElement, 'title')?.text,
-      author: findFirstElement(channelElement, 'author')?.text,
-      description: findFirstElement(channelElement, 'description')?.text,
-      link: findFirstElement(channelElement, 'link')?.text,
-      items: (rss != null ? channelElement : rdf)!
+      title: channelElement.findElements('title').firstOrNull?.text,
+      author: channelElement.findElements('author').firstOrNull?.text,
+      description: channelElement.findElements('description').firstOrNull?.text,
+      link: channelElement.findElements('link').firstOrNull?.text,
+      items: (rdf ?? channelElement)
           .findElements('item')
           .map((e) => RssItem.parse(e))
           .toList(),
-      image: RssImage.parse(
-          findFirstElement(rss != null ? channelElement : rdf, 'image')),
-      cloud: RssCloud.parse(findFirstElement(channelElement, 'cloud')),
+      image: (rdf ?? channelElement)
+          .findElements('image')
+          .map((e) => RssImage.parse(e))
+          .firstOrNull,
+      cloud: channelElement
+          .findElements('cloud')
+          .map((e) => RssCloud.parse(e))
+          .firstOrNull,
       categories: channelElement
           .findElements('category')
           .map((e) => RssCategory.parse(e))
           .toList(),
-      skipDays: findFirstElement(channelElement, 'skipDays')
+      skipDays: channelElement
+              .findElements('skipDays')
+              .firstOrNull
               ?.findAllElements('day')
               .map((e) => e.text)
               .toList() ??
           [],
-      skipHours: findFirstElement(channelElement, 'skipHours')
+      skipHours: channelElement
+              .findElements('skipHours')
+              .firstOrNull
               ?.findAllElements('hour')
-              .map((e) => int.tryParse(e.text))
+              .map((e) => int.tryParse(e.text) ?? 0)
               .toList() ??
           [],
-      lastBuildDate: findFirstElement(channelElement, 'lastBuildDate')?.text,
-      language: findFirstElement(channelElement, 'language')?.text,
-      generator: findFirstElement(channelElement, 'generator')?.text,
-      copyright: findFirstElement(channelElement, 'copyright')?.text,
-      docs: findFirstElement(channelElement, 'docs')?.text,
-      managingEditor: findFirstElement(channelElement, 'managingEditor')?.text,
-      rating: findFirstElement(channelElement, 'rating')?.text,
-      webMaster: findFirstElement(channelElement, 'webMaster')?.text,
-      ttl: int.tryParse(findFirstElement(channelElement, 'ttl')?.text ?? '0'),
+      lastBuildDate:
+          channelElement.findElements('lastBuildDate').firstOrNull?.text,
+      language: channelElement.findElements('language').firstOrNull?.text,
+      generator: channelElement.findElements('generator').firstOrNull?.text,
+      copyright: channelElement.findElements('copyright').firstOrNull?.text,
+      docs: channelElement.findElements('docs').firstOrNull?.text,
+      managingEditor:
+          channelElement.findElements('managingEditor').firstOrNull?.text,
+      rating: channelElement.findElements('rating').firstOrNull?.text,
+      webMaster: channelElement.findElements('webMaster').firstOrNull?.text,
+      ttl: int.tryParse(
+          channelElement.findElements('ttl').firstOrNull?.text ?? '0'),
       dc: DublinCore.parse(channelElement),
       itunes: Itunes.parse(channelElement),
       syndication: Syndication.parse(channelElement),

lib/domain/rss_image.dart

@@ -1,4 +1,4 @@
-import 'package:webfeed/util/xml.dart';
+import 'package:webfeed/util/iterable.dart';
 import 'package:xml/xml.dart';
 
 class RssImage {
@@ -8,12 +8,11 @@ class RssImage {
 
   RssImage({this.title, this.url, this.link});
 
-  static parse(XmlElement? element) {
-    if (element == null) return null;
+  factory RssImage.parse(XmlElement element) {
     return RssImage(
-      title: findFirstElement(element, 'title')?.text,
-      url: findFirstElement(element, 'url')?.text,
-      link: findFirstElement(element, 'link')?.text,
+      title: element.findElements('title').firstOrNull?.text,
+      url: element.findElements('url').firstOrNull?.text,
+      link: element.findElements('link').firstOrNull?.text,
     );
   }
 }

lib/domain/rss_item.dart

@@ -6,7 +6,7 @@ import 'package:webfeed/domain/rss_content.dart';
 import 'package:webfeed/domain/rss_enclosure.dart';
 import 'package:webfeed/domain/rss_source.dart';
 import 'package:webfeed/util/datetime.dart';
-import 'package:webfeed/util/xml.dart';
+import 'package:webfeed/util/iterable.dart';
 import 'package:xml/xml.dart';
 
 class RssItem {
@@ -14,7 +14,7 @@ class RssItem {
   final String? description;
   final String? link;
 
-  final List<RssCategory?>? categories;
+  final List<RssCategory>? categories;
   final String? guid;
   final DateTime? pubDate;
   final String? author;
@@ -45,21 +45,30 @@ class RssItem {
 
   factory RssItem.parse(XmlElement element) {
     return RssItem(
-      title: findFirstElement(element, 'title')?.text,
-      description: findFirstElement(element, 'description')?.text,
-      link: findFirstElement(element, 'link')?.text,
+      title: element.findElements('title').firstOrNull?.text,
+      description: element.findElements('description').firstOrNull?.text,
+      link: element.findElements('link').firstOrNull?.text,
       categories: element
           .findElements('category')
           .map((e) => RssCategory.parse(e))
           .toList(),
-      guid: findFirstElement(element, 'guid')?.text,
-      pubDate: parseDateTime(findFirstElement(element, 'pubDate')?.text),
-      author: findFirstElement(element, 'author')?.text,
-      comments: findFirstElement(element, 'comments')?.text,
-      source: RssSource.parse(findFirstElement(element, 'source')),
-      content: RssContent.parse(findFirstElement(element, 'content:encoded')),
+      guid: element.findElements('guid').firstOrNull?.text,
+      pubDate: parseDateTime(element.findElements('pubDate').firstOrNull?.text),
+      author: element.findElements('author').firstOrNull?.text,
+      comments: element.findElements('comments').firstOrNull?.text,
+      source: element
+          .findElements('source')
+          .map((e) => RssSource.parse(e))
+          .firstOrNull,
+      content: element
+          .findElements('content:encoded')
+          .map((e) => RssContent.parse(e))
+          .firstOrNull,
       media: Media.parse(element),
-      enclosure: RssEnclosure.parse(findFirstElement(element, 'enclosure')),
+      enclosure: element
+          .findElements('enclosure')
+          .map((e) => RssEnclosure.parse(e))
+          .firstOrNull,
       dc: DublinCore.parse(element),
       itunes: Itunes.parse(element),
     );

lib/domain/rss_source.dart

@@ -6,8 +6,7 @@ class RssSource {
 
   RssSource(this.url, this.value);
 
-  static parse(XmlElement? element) {
-    if (element == null) return null;
+  factory RssSource.parse(XmlElement element) {
     var url = element.getAttribute('url');
     var value = element.text;
 

lib/domain/syndication/syndication.dart

@@ -1,5 +1,5 @@
 import 'package:webfeed/util/datetime.dart';
-import 'package:webfeed/util/xml.dart';
+import 'package:webfeed/util/iterable.dart';
 import 'package:xml/xml.dart';
 
 enum SyndicationUpdatePeriod { hourly, daily, weekly, monthly, yearly }
@@ -15,10 +15,9 @@ class Syndication {
     this.updateBase,
   });
 
-  static parse(XmlElement? element) {
-    if (element == null) return null;
+  factory Syndication.parse(XmlElement element) {
     SyndicationUpdatePeriod updatePeriod;
-    switch (findFirstElement(element, 'sy:updatePeriod')?.text) {
+    switch (element.findElements('sy:updatePeriod').firstOrNull?.text) {
       case 'hourly':
         updatePeriod = SyndicationUpdatePeriod.hourly;
         break;
@@ -41,9 +40,9 @@ class Syndication {
     return Syndication(
       updatePeriod: updatePeriod,
       updateFrequency: int.tryParse(
-          findFirstElement(element, 'sy:updateFrequency')?.text ?? '1'),
-      updateBase:
-          parseDateTime(findFirstElement(element, 'sy:updateBase')?.text),
+          element.findElements('sy:updateFrequency').firstOrNull?.text ?? '1'),
+      updateBase: parseDateTime(
+          element.findElements('sy:updateBase').firstOrNull?.text),
     );
   }
 }

lib/util/iterable.dart

@@ -0,0 +1,3 @@
+extension WebFeedIterable<T> on Iterable<T> {
+  T? get firstOrNull => isEmpty ? null : first;
+}

lib/util/xml.dart

@@ -1,21 +1,8 @@
 import 'dart:core';
 
+import 'package:webfeed/util/iterable.dart';
 import 'package:xml/xml.dart';
 
-XmlElement? findFirstElement(
-  XmlNode? node,
-  String name, {
-  bool recursive = false,
-  String? namespace,
-}) {
-  try {
-    return findElements(node, name, recursive: recursive, namespace: namespace)
-        ?.first;
-  } on StateError {
-    return null;
-  }
-}
-
 Iterable<XmlElement>? findElements(
   XmlNode? node,
   String name, {
@@ -34,7 +21,7 @@ Iterable<XmlElement>? findElements(
 }
 
 bool parseBoolLiteral(XmlElement element, String tagName) {
-  var v = findFirstElement(element, tagName)?.text.toLowerCase().trim();
+  var v = element.findElements(tagName).firstOrNull?.text.toLowerCase().trim();
   if (v == null) return false;
   return ['yes', 'true'].contains(v);
 }

test/atom_test.dart

@@ -185,9 +185,9 @@ void main() {
     expect(item.media!.embed!.width, 512);
     expect(item.media!.embed!.height, 323);
     expect(item.media!.embed!.params!.length, 5);
-    expect(item.media!.embed!.params!.first!.name, 'type');
-    expect(
-        item.media!.embed!.params!.first!.value, 'application/x-shockwave-flash');
+    expect(item.media!.embed!.params!.first.name, 'type');
+    expect(item.media!.embed!.params!.first.value,
+        'application/x-shockwave-flash');
 
     expect(item.media!.responses!.length, 2);
     expect(item.media!.responses!.first, 'http://www.response1.com');
@@ -203,8 +203,8 @@ void main() {
     expect(item.media!.prices!.length, 2);
     expect(item.media!.prices!.first.price, 19.99);
     expect(item.media!.prices!.first.type, 'rent');
-    expect(
-        item.media!.prices!.first.info, 'http://www.dummy.jp/package_info.html');
+    expect(item.media!.prices!.first.info,
+        'http://www.dummy.jp/package_info.html');
     expect(item.media!.prices!.first.currency, 'EUR');
 
     expect(item.media!.license!.type, 'text/html');
@@ -218,10 +218,10 @@ void main() {
     expect(item.media!.rights!.status, 'official');
 
     expect(item.media!.scenes!.length, 2);
-    expect(item.media!.scenes!.first!.title, 'sceneTitle1');
-    expect(item.media!.scenes!.first!.description, 'sceneDesc1');
-    expect(item.media!.scenes!.first!.startTime, '00:15');
-    expect(item.media!.scenes!.first!.endTime, '00:45');
+    expect(item.media!.scenes!.first.title, 'sceneTitle1');
+    expect(item.media!.scenes!.first.description, 'sceneDesc1');
+    expect(item.media!.scenes!.first.startTime, '00:15');
+    expect(item.media!.scenes!.first.endTime, '00:45');
   });
 
   test('parse Atom-Empty.xml', () {

test/rss_test.dart

@@ -47,10 +47,10 @@ void main() {
     expect(feed.cloud!.protocol, 'xml-rpc');
 
     expect(feed.categories!.length, 2);
-    expect(feed.categories![0]!.domain, null);
-    expect(feed.categories![0]!.value, 'Ipsum');
-    expect(feed.categories![1]!.domain, 'news');
-    expect(feed.categories![1]!.value, 'Lorem Ipsum');
+    expect(feed.categories![0].domain, null);
+    expect(feed.categories![0].value, 'Ipsum');
+    expect(feed.categories![1].domain, 'news');
+    expect(feed.categories![1].value, 'Lorem Ipsum');
 
     expect(feed.skipDays!.length, 3);
     expect(feed.skipDays!.contains('Monday'), true);
@@ -74,8 +74,8 @@ void main() {
     expect(feed.items!.first.guid, 'https://foo.bar.news/1?guid');
     expect(feed.items!.first.pubDate,
         DateTime(2018, 03, 26, 14)); //Mon, 26 Mar 2018 14:00:00 PDT
-    expect(feed.items!.first.categories!.first!.domain, 'news');
-    expect(feed.items!.first.categories!.first!.value, 'Lorem');
+    expect(feed.items!.first.categories!.first.domain, 'news');
+    expect(feed.items!.first.categories!.first.value, 'Lorem');
     expect(feed.items!.first.author, 'alice@foo.bar.news');
     expect(feed.items!.first.source!.url, 'https://foo.bar.news/1?source');
     expect(feed.items!.first.source!.value, 'Foo Bar');
@@ -192,9 +192,9 @@ void main() {
     expect(item.media!.embed!.width, 512);
     expect(item.media!.embed!.height, 323);
     expect(item.media!.embed!.params!.length, 5);
-    expect(item.media!.embed!.params!.first!.name, 'type');
-    expect(
-        item.media!.embed!.params!.first!.value, 'application/x-shockwave-flash');
+    expect(item.media!.embed!.params!.first.name, 'type');
+    expect(item.media!.embed!.params!.first.value,
+        'application/x-shockwave-flash');
 
     expect(item.media!.responses!.length, 2);
     expect(item.media!.responses!.first, 'http://www.response1.com');
@@ -210,8 +210,8 @@ void main() {
     expect(item.media!.prices!.length, 2);
     expect(item.media!.prices!.first.price, 19.99);
     expect(item.media!.prices!.first.type, 'rent');
-    expect(
-        item.media!.prices!.first.info, 'http://www.dummy.jp/package_info.html');
+    expect(item.media!.prices!.first.info,
+        'http://www.dummy.jp/package_info.html');
     expect(item.media!.prices!.first.currency, 'EUR');
 
     expect(item.media!.license!.type, 'text/html');
@@ -225,10 +225,10 @@ void main() {
     expect(item.media!.rights!.status, 'official');
 
     expect(item.media!.scenes!.length, 2);
-    expect(item.media!.scenes!.first!.title, 'sceneTitle1');
-    expect(item.media!.scenes!.first!.description, 'sceneDesc1');
-    expect(item.media!.scenes!.first!.startTime, '00:15');
-    expect(item.media!.scenes!.first!.endTime, '00:45');
+    expect(item.media!.scenes!.first.title, 'sceneTitle1');
+    expect(item.media!.scenes!.first.description, 'sceneDesc1');
+    expect(item.media!.scenes!.first.startTime, '00:15');
+    expect(item.media!.scenes!.first.endTime, '00:45');
   });
   test('parse RSS-DC.xml', () {
     var xmlString = File('test/xml/RSS-DC.xml').readAsStringSync();
@@ -332,12 +332,12 @@ void main() {
     expect(feed.itunes!.owner!.email, 'editors@changelog.com');
     expect(
         Set.from([
-          feed.itunes!.categories![0]!.category,
-          feed.itunes!.categories![1]!.category
+          feed.itunes!.categories![0].category,
+          feed.itunes!.categories![1].category
         ]),
         ['Technology', 'Foo']);
     for (var category in feed.itunes!.categories!) {
-      switch (category!.category) {
+      switch (category.category) {
         case 'Foo':
           expect(category.subCategories, ['Bar', 'Baz']);
           break;