在 firebase 中添加所有数字并将其存储在 Flutter 中的变量中

Question

我有一个带有评级字段的集合，我想遍历集合并添加所有值。最后，我想将它存储在一个变量中，该变量可以被所有屏幕在颤动中访问。

有什么想法吗？

这是我尝试过的但失败了

void calculateHomeTeamRating(){
    int rating=0;
    StreamBuilder<QuerySnapshot>(
      stream: _firestore.collection('SelectedPlayersHome').snapshots(),
      builder: (context, snapshot){
        if(!snapshot.hasData){
          return Center(
            child: CircularProgressIndicator(
              backgroundColor: Colors.lightBlueAccent,
            ),
          );
        }
        final players = snapshot.data.docs;
        List<int> homeRating = [];
        for(var playerRating in players){
          rating = rating + playerRating.get('Rating');
        }
        String textRating = rating.toString();
        homeRating.add(rating);
        return null;
      },
    );
  }
}

这是显示玩家姓名和评分的集合和字段：

Answer 1

您可以创建一个模型类来对来自 firestore 的传入数据进行编码和解码，并且可以使用此模型类来存储数据。

创建类来存储玩家数据。

class Player {
  String playerName;
  int rating;
  String timestamp;

  Player({this.playerName, this.rating, this.timestamp});

  Player.fromJson(Map<String, dynamic> json) {
    playerName = json['PlayerName'];
    rating = json['Rating'];
    timestamp = json['timestamp'];
  }

  Map<String, dynamic> toJson() {
    final Map<String, dynamic> data = new Map<String, dynamic>();
    data['PlayerName'] = this.playerName;
    data['Rating'] = this.rating;
    data['timestamp'] = this.timestamp;
    return data;
  }
}

将QuerySnapshot 传递给calculateHomeTeamRating 函数，它将返回List<Player> 并相应地使用它。 .

Future<List<Player>> calculateHomeTeamRating(
      QuerySnapshot querySnapshot) async {
    final List<Player> playerList = [];

    final data = querySnapshot.docs;
    if (data != null && data.isNotEmpty) {
      for (var i = 0; i < data.length; i++) {
        var model = Player.fromJson(querySnapshot.docs[i].data());
        playerList.add(model);
      }
      return playerList;
    } else {
      return null;
      
    }
  }
}

使用玩家列表中的特定值（评分）

var List<int> ratings;

final players = snapshot.data.docs;

final list = calculateHomeTeamRating(players);

if(list!= null && list.isNotEmpty){
  ratings = list.map((player)=> player.rating).toList();
}

if(ratings!= null && ratings.isNotEmpty){
  print("Total given ratings: ${ratings.length}");
}