javascript - 未处理的 promise 拒绝 : Cannot call method 'push' of null

Question

我有一个我似乎无法理解的问题。如果有人可以提供一些建议，我将不胜感激。

我正在使用 Ionic2 和 Meteor/Mongo 构建一个聊天应用程序。

我有以下代码:

  private findChats(): Promise<Mongo.Collection<Chat>> {
    let promise: Promise<Mongo.Collection<Chat>> = new Promise<Mongo.Collection<Chat>>(resolve => {
      let registeredIds: String[] = [this.senderId];
      for (let i = 0; i < this.jobModelsForSender.length; i++) {
        console.log('findChats:  registeredIds.push this.jobModelsForSender[i].id: ' + registeredIds + '  -  ' + this.jobModelsForSender[i].id);
        registeredIds.push('J' + this.jobModelsForSender[i].id);
        console.log('findChats:  pushed: ' + registeredIds);
      }
      this.subscribe('chats', this.senderId, registeredIds, () => {
        console.log('findChats:  in subscribe: ' + this.senderId+'  '+registeredIds);

        let chats: Mongo.Cursor<Chat> = Chats.find(
          { memberIds: { $in: registeredIds } },
          {
            sort: { lastMessageCreatedAt: -1 },
            transform: this.transformChat.bind(this),
            fields: { memberIds: 1, lastMessageCreatedAt: 1 }
          }
        );
        console.log('findChats:  chats: ' + chats);
        this.chats = chats;
        let localChatCollection: Mongo.Collection<Chat> = new Mongo.Collection<Chat>(null);
        chats.forEach((chat: Chat) => {
          localChatCollection.insert(chat);
        });
        console.log('findChats:  resolve(localChatCollection): ' + localChatCollection);
        resolve(localChatCollection);
      });
    });
    return promise;
  }

但我得到以下输出:

findChats:  registeredIds.push this.jobModelsForSender[i].id: P8  -  72 app.bundle.js:118232
findChats:  pushed: P8,J72 app.bundle.js:118234
findChats:  registeredIds.push this.jobModelsForSender[i].id: P8  -  72 app.bundle.js:118232
findChats:  pushed: P8,J72 app.bundle.js:118234
findChats:  registeredIds.push this.jobModelsForSender[i].id: P8  -  72 app.bundle.js:118232
findChats:  pushed: P8,J72 app.bundle.js:118234
Unhandled Promise rejection: Cannot call method 'push' of null ; Zone: <root> ; Task: Promise.then ; Value: TypeError {stack: (...), message: "Cannot call method 'push' of null"} zone.js:461
Error {rejection: TypeError, promise: ZoneAwarePromise, zone: Zone, task: ZoneTask, stack: (...)…}
 zone.js:463
Unhandled Promise rejection: Cannot call method 'push' of null ; Zone: <root> ; Task: Promise.then ; Value: TypeError {stack: (...), message: "Cannot call method 'push' of null"} zone.js:461
Error {rejection: TypeError, promise: ZoneAwarePromise, zone: Zone, task: ZoneTask, stack: (...)…}
 zone.js:463
Unhandled Promise rejection: Cannot call method 'push' of null ; Zone: <root> ; Task: Promise.then ; Value: TypeError {stack: (...), message: "Cannot call method 'push' of null"} zone.js:461
Error {rejection: TypeError, promise: ZoneAwarePromise, zone: Zone, task: ZoneTask, stack: (...)…}
 zone.js:463
findChats:  in subscribe: P8  P8,J72 app.bundle.js:118243
findChats:  chats: [object Object] app.bundle.js:118249
findChats:  resolve(localChatCollection): [object Object] 

如您所见，我在 zone.js 中遇到错误。据我所知，当我调试它时，如日志所示，它成功地将 push 发送到 registeredIds。然后它退出函数，返回 promise。之后它进入记录错误的 zone.js。

Answer 1

答案可能与很多人无关，但正如安东指出的那样，这是一个与异步加载 promise 有关的问题。

我有一个事件同时调用同一个 promise 。一旦我删除该事件的触发器，我就不会收到任何错误。