Flutter null 安全问题是：未为类型 'Object' 定义运算符 '[]'

Question

问题是空安全和迁移如何解决运算符'[]'没有为类型'Object'

定义

```
import 'package:cloud_firestore/cloud_firestore.dart';

 class UserModel {
  static const NUMBER = 'number';
  static const ID = 'id';

 late String _number;
 late String _id;

//getter

 String get number => _number;
 String get id => _id;

 UserModel.fromSnapshot(DocumentSnapshot snapshot) {
  _number = snapshot.data()![NUMBER];
  _id = snapshot.data()![ID];
 }
}
```

Answer 1

解决方案就是像这样更明确地定义 CollectionReference：

 UserModel.fromSnapshot(DocumentSnapshot<Map<String, dynamic>> snapshot) {
  _number = snapshot.data()![NUMBER];
  _id = snapshot.data()![ID];
 }
}

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Flutter null 安全问题是：未为类型 'Object' 定义运算符 '[]'

Flutter null safety problem is : The operator '[]' isn't defined for the type 'Object'

null

dart

flutter