firebase-realtime-database - Flutter firebase 数据库迭代项目

Question

我想知道如何从 Flutter 上的路径中获取对象列表，这是我获取一个对象并且工作正常的方法：

static Future<Year> getYear(
  String yearKey) async {
Completer<Year> completer = new Completer<Year>();

FirebaseDatabase.instance
    .reference()
    .child("year")
    .child(yearKey)
    .once()
    .then((DataSnapshot snapshot) {

  var year = new Year.fromJson(snapshot.key, snapshot.value);

  completer.complete(year);
});

return completer.future;
}

现在我正在尝试以这种方式获取同一路径中所有年份的列表，但不知道如何迭代项目：

static Future<List<Year>> getYears() async {
    Completer<List<Year>> completer = new Completer<List<Year>>();

    List<Year> years = new List<Year>();

    FirebaseDatabase.instance
        .reference()
        .child("year")
        .once()
        .then((DataSnapshot snapshot) {

        //how to iterate over the items here?

      completer.complete(years);
    });

    return completer.future;
  }

请有人帮助我。

标签： firebase-realtime-databasedartflutter

Answer 1

对于有同样问题的人，我得到了这个工作：

static Future<List<Year>> getYears() async {
    Completer<List<Year>> completer = new Completer<List<Year>>();

    List<Year> years = new List<Year>();

    FirebaseDatabase.instance
        .reference()
        .child("year")
        .once()
        .then((DataSnapshot snapshot) {
          //here i iterate and create the list of objects
          Map<dynamic, dynamic> yearMap = snapshot.value;
          yearMap.forEach((key, value) {
            years.add(Year.fromJson(key, value));
          });

      completer.complete(years);
    });

    return completer.future;
  }

这是年份代码：

class Year{
  String key;
  String name;

  Year({this.name});

  Year.fromJson(this.key, Map data){
    name = data['name'];
    if(name == null){
      name = '';
    }
  }
}

谢谢大家。