爲什麼即使初始化爲數組後，Typescript仍然無法讀取推式方法？ （ANGULAR2）

Question

我試圖創建一個使用pubnub和Angular2的聊天應用程序，但我堅持在這一部分。

import { Injectable } from '@angular/core'; 
import { PubNubAngular } from 'pubnub-angular2'; 

@Injectable() 
export class ChatService { 
    public uuid: string; 
    public message: string; 
    public messages = []; <------------------- Already initialized 
    public channel: string[]; 

    constructor(private pubnub:PubNubAngular) { 

    // ....... /// 

    this.pubnub.addListener({ 
     message: function (m) { 
     let msg: object = { 
      origin: m.channel, 
      timetoken: m.timetoken, 
      content: m.message, 
      sender: m.sender 
     } 
     this.messages.push(msg); <-------- PRODUCES A "CANNOT READ PROPERTY 
              'PUSH' OF TYPE UNDEFINED IN [NULL]" ERROR 
     } 
    }); 
    } 

請幫幫忙，這似乎出於某種原因我不能訪問該部分消息數組，大概是爲什麼它不能檢測push方法。

Answer 1

使用箭頭功能應該能夠解決您的問題

message: (m) => { 
    let msg: object = { 
    origin: m.channel, 
    timetoken: m.timetoken, 
    content: m.message, 
    sender: m.sender 
    } 
    this.messages.push(msg); <-------- now this is your component instance 
} 

查看關於箭頭的功能在這裏

• https://developer.mozilla.org/en/docs/Web/JavaScript/Reference/Functions/Arrow_functions#No_binding_of_this