从 Observable Array of Objects 迭代 *ngFor 时如何修复 InvalidPipeArgument 错误

Question

尝试从 Observable Array of Objects 迭代 *ngFor 时出错

我使用 Angular 8

聊天消息服务

private chatMessages = [];
private chatMessagesStream = new BehaviorSubject(this.chatMessages);

getMessages(): Observable<any> {
   return this.chatMessagesStream.asObservable();
}


addMessage(chatMessage) {
    this.chatMessages.push(chatMessage);
    this.chatMessagesStream.next(this.chatMessages);
}

聊天视图组件

private chatMessages:Observable<Array<any>>;

constructor(
   private chatMessagesService: ChatMessagesService) {
}

ngAfterViewInit() {
    this.chatMessagesService.getMessages().subscribe(messages => {
      this.chatMessages = messages;
      this.scrollMessagesToBottom(true);
    });
}

聊天 HTML 模板

<div class="row conpeek_message_chat_row" *ngFor="let chatMessage of chatMessages | async ">
...
</div>

在初始化组件之后，我在控制台中遇到了问题，可能是什么问题？

ERROR Error: InvalidPipeArgument: '[object Object]' for pipe 'AsyncPipe'

Answer 1

移除异步管道

由于chatMessages不可观察，它包含纯值。

this.chatMessagesService.getMessages().subscribe(messages => {
    this.chatMessages = messages; // <------- HERE , you are assigning value
    this.scrollMessagesToBottom(true);
});

---

如果你想保持异步管道，你必须将chatMessages分配给observable，像这样：

this.chatMessages = this.chatMessagesService.getMessages();