Flutter 2.0：如何为 firestore 快照创建模型类

Question

如何为 flutter 2.0 的 firestore 快照构建 flutter 类

我尝试过这样的事情：

import 'package:cloud_firestore/cloud_firestore.dart';

class Post {
  final String pid;
  final String description;

  final DocumentReference reference;

  Post.fromMap(Map<String, dynamic> map, this.pid, this.description, {required this.reference})

  Post.fromSnapshot(DocumentSnapshot snapshot)
      : this.fromMap(snapshot.data(), reference: snapshot.reference);

  @override
  String toString() => "Post<$pid:$description>";
}

但出现错误，指出需要 3 个位置参数，但找到了 1 个。

Answer 1

您没有传递pid和description（这是位置参数）。您可以将它们设为可选的命名参数或显式传递它们。

解决方案1（使参数可选）：

class Post {
  final String pid;
  final String description;
  final DocumentReference reference;

  Post.fromSnapshot(DocumentSnapshot snapshot)
      : this.fromMap(
          snapshot.data() as Map<String, dynamic>,
          reference: snapshot.reference,
        );

  Post.fromMap(
    Map<String, dynamic> map, {
    required this.reference,
    this.pid = 'dummyID',
    this.description = 'dummyDesc',
  });

  @override
  String toString() => 'Post<$pid:$description>';
}

解决方案2（传递参数）：

class Post {
  final String pid;
  final String description;
  final DocumentReference reference;

  Post.fromSnapshot(DocumentSnapshot snapshot)
      : this.fromMap(
          snapshot.data() as Map<String, dynamic>,
          'pid',
          'description',
          reference: snapshot.reference,
        );

  Post.fromMap(
    Map<String, dynamic> map,
    this.pid,
    this.description, {
    required this.reference,
  });

  @override
  String toString() => 'Post<$pid:$description>';
}