Question

我正在尝试在服务类中实现一个回调函数，该函数必须将数据返回给组件类。

ChatComponent.ts

export class ChatComponent implements OnInit {

  constructor( public _chatService : ChatService) {
    _chatService.joinChat()
  }

  OnInit(){

  }

 // I need to get the `msg` object from the ChatService class
  didReceiveMessage(msg){
console.log(“Message received from chat service class”+msg);
  } 

}

ChatService.ts

import { Component, Input } from '@angular/core';
import { Injectable }     from '@angular/core';


@Injectable()
export class ChatService {
   public chatObj : SomeChatObject;

    constructor() { }

    joinChat(){
    //Join chat related functionality
    this.chatObj.addHandler(this.onMessageReceivedHandler, null, "message");
    }

     onMessageReceivedHandler = (message) => {
    //Send `message` back to `didReceiveMessage ` method in ChatComponent.ts
     return true;
     }
}

我见过使用Http Observable回调的例子。在这里，我使用addHandler显式添加了我的回调。我将在'onMessageReceivedHandler'方法中获取消息对象。但我需要将它传递给ChatComponent。我如何传递数据。

Answer 1

我认为Carsten是对的，你可以使用主题和行为主题来获得按摩

在服务档案

中

message:Subject<string> = new Subject();

    broadcastMessage(text:string) {
        this.message.next(text);
    }

并在组件文件中，您可以订阅邮件主题

this. _chatService.message.subscribe((msg) => {
  console.log(“Message received from chat service class”+msg);
});

Answer 2

您可以使用主题。

在ChatService中：

subscribers: Subject[] = [];

然后在joinChat

joinChat(userSubject: Subject) {
  this.subscribers.push(userSubject);
}

然后在messageReceivedHandler中：

for (let i = 0; i < this.subscribers.length(); i++) {
  this.subscribers[i].next("Hello");
}

ChatComponent：

constructor( public _chatService : ChatService) {
  let subject = new Subject();
  subject.subscribe(
    msg => console.log(msg);
  );

  _chatService.joinChat(subject);
}

请注意：我是从头开始写的，所以不能保证代码编译..

在回调函数中可观察 - angular 2

2 个答案: