如何将 Firebase 数据作为 Querysnapshot 获取？

Question

我试图从 firebase 获取 Array 作为 Flutter 的 Querysnaoshot，但我该怎么做？ 这是代码

class Videos {
  final String allhashtagsofeveryvideo;
  final String categorie;
  final String commentcount;
  final String hashtag1;
  final String hashtag2;
  final String hashtag3;
  final String likes;
  final String previewimage;
   final String profilepic;
  final String sharecount;
  final String uid;
  final String username;
  final String videourl;

  Videos( {this.allhashtagsofeveryvideo,this.commentcount, this.hashtag1, this.hashtag2, this.hashtag3, this.likes, this.previewimage, this.profilepic, this.sharecount, this.uid, this.videourl, this.categorie, this.username});
}

 Videos videosfromsnapshot(DocumentSnapshot snapshot) {
    return Videos(
      categorie: snapshot.data()['categorie'],
      commentcount: snapshot.data()['commentcount'].toString(),
      hashtag1: snapshot.data()['hashtag1'],
      hashtag2: snapshot.data()['hashtag2'],
      hashtag3: snapshot.data()['hashtag3'],
      likes:snapshot.data()['likes'].length.toString(),
      previewimage: snapshot.data()['previewimage'],
      profilepic: snapshot.data()['profilepic'],
      sharecount: snapshot.data()['sharecount'].toString(),
      uid: snapshot.data()['uid'],
      allhashtagsofeveryvideo:snapshot.data()['Hashtagsforallvideos'],
      username: snapshot.data()['username'],
      videourl: snapshot.data()['videourl'],
    );
  }
 var firestore = FirebaseFirestore.instance;
  List<QueryDocumentSnapshot> _allResults = [];

    QuerySnapshot snapshots = await firestore.collection('videos').get();
    for (var doc in snapshots.docs) {
     
      _allResults.addAll(doc.data()["Hashtagsforallvideos"]);

也许我应该映射它或类似的东西？ 所以不要像你看到的那样添加它，我想那样使用

 QuerySnapshot snapshots = await firestore.collection('videos').get();
    for (var doc in snapshots.docs) {

....
 _allResults= qn.docs 

但是我该怎么做也许有人可以提供帮助 我没有收到此错误

[VERBOSE-2:ui_dart_state.cc(186)] Unhandled Exception: type 'List<dynamic>' is not a subtype of type 'QueryDocumentSnapshot'
#0      _OpenallsinglehashtagsState.getusers
package:wichtigdenyady/homesearchingall/openalldocs.dart:90
<asynchronous suspension>

这一行就是这一行

 _allResults.addAll(doc.data()["Hashtagsforallvideos"]);

大概是这样的

  var firestore = FirebaseFirestore.instance;
    QuerySnapshot qn = await firestore.collection('videos').get();
    if (!mounted) return;

    setState(() {
      _allResults = qn.docs;
    });

Answer 1

没有数据有点困难，但我希望这可以帮助你：

Future<List<QueryDocumentSnapshot>> getVideos() async {
  List<String> allVideoHastags = [];
  List<QueryDocumentSnapshot> _allResults = [];

  QuerySnapshot snapshots = await _firestore.collection('videos').get();

  for (QueryDocumentSnapshot videoSnapshot in snapshots.docs) {
    List<String> videoHastags =
        List.from(videoSnapshot.data()['Hashtagsforallvideos']);
    allVideoHastags.addAll(videoHastags);
    _allResults.add(videoSnapshot);
  }

  return _allResults;
}

在大多数情况下，当我们使用 Firestore 数组并在 List 中需要它们时，我们会错过 List.from 构造函数。