firebase - Flutter Firestore StreamTransformer DocumentSnapshot错误

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The argument type 'Map<String, dynamic> Function()' can't be assigned to the parameter type 'Map<String, dynamic>'

(2个答案)


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我曾经练习Flutter用firestore开发一个简单的实时聊天应用程序，之前我使用cloud_firestore 0.13.7并运行良好。更新到cloud_firestore 0.14.0 + 2的新版本后，我不确定该如何修改代码中的重大更改。
repository_service.dart

class RepositoryService {
final CollectionReference _usersCollectionReference =
      FirebaseFirestore.instance.collection('users');

Stream<DocumentSnapshot> getChatList(String id) {
    return _userChatsCollectionReference.doc(id).snapshots();
  }
}

chat_services.dart

class chat_services(){

RepositoryService _repositoryService = locator<RepositoryService>();

Stream<List<String>> getChatList(String id) {
    return _repositoryService.getChatList(id).transform(documentToChatListTransformer);
  }

  StreamTransformer documentToChatListTransformer = StreamTransformer<DocumentSnapshot, List<String>>.fromHandlers(
    handleData: (DocumentSnapshot snapShot, EventSink<List<String>> sink) {
      if (snapShot.exists) {
        sink.add(snapShot.data.keys.toList());
      } else {
        sink.add([]);
      }
    }
  );

}

错误是 键，它来自chat_services.dart中的函数 documentToChatListTransformer

The getter 'keys' isn't defined for the type 'Map<String, dynamic>Function()'. Try importing the library that defines 'keys', correctingthe name to the name of an existing getter, or defining a getter orfield named 'keys'.dart(undefined_getter)

最佳答案

在这里，data是method on DocumentSnapshot，而不是属性。您需要使用括号来调用该方法:

snapShot.data().keys.toList()

关于firebase - Flutter Firestore StreamTransformer DocumentSnapshot错误，我们在Stack Overflow上找到一个类似的问题： https://stackoverflow.com/questions/64040848/

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Answer 1

在这里，data是method on DocumentSnapshot，而不是属性。您需要使用括号来调用该方法:

snapShot.data().keys.toList()