Question

我的组件中有以下代码，而ionViewDidLoad方法中的chats.push（）函数会生成错误：

@Component({
  selector: 'page-messages',
  templateUrl: 'messages.html'
})
export class MessagesPage {

  currentUser: User;
  chats: Chat[];

  constructor(public navCtrl: NavController, public navParams: NavParams, private _auth: AuthService, private _db: DatabaseService, private _user: UserService) {

    console.log('constructor MessagesPage');

    // Get currently authenticated user
    this.currentUser = this._auth.currentUser;
  }

  ionViewDidLoad() {
    //console.log(this.chats.length);

    console.log('ionViewDidLoad MessagesPage');

    // Load chats
    this._user.getChatsAsObservableList(this.currentUser.uid).subscribe(tmpChats => {

      tmpChats.forEach(tmpChat => {

        console.log(tmpChat);
        // Retrieve chat id
        let chatId = tmpChat.$key;
        console.log('Retrieving a chat with id ', chatId);

        // Instantiate a Chat object
        let chat = new Chat(chatId, tmpChat);

        // Retrieve its members
        let chatMembers = this._db.getChatMembersAsObservableList(chatId);
        // For each member retrieve the user info and add it the members of the Chat object
        chatMembers.subscribe(members => {
          members.forEach(member => {
            this.addMemberToChat(chatId, member.$key);
          });
        });

        // finally add the chat to the chat list
        this.chats.push(chat); // Generates an ERROR : Cannot read property 'push' of undefined
        console.log('Chat:', chat);
      });
    });
  }

  // Methods
  addMemberToChat(chat: Chat, uid: string) {
    if (uid) {
      let userAsObservableObj = this._user.getUserAsObservableObj(uid);
      let user = new User(uid, userAsObservableObj);
      chat.members.push(user);
    } else {
      console.log('Could not add member to Chat object because uid was empty.');
    }
  }

}

我想这是一个＆＃34;这个＆＃34;问题，我看到很多关于这个的帖子，但我无法用胖箭解决它。我想这是因为我有几个承诺......

我怎么解决这个问题？

Answer 1

初始化聊天解决了这个问题：

chats: Chat[] = [];

在ionViewDidLoad（）中的subscribe（）内访问组件变量

1 个答案: