EventEmitter in shared service's constructor doens't emit data

问题

I have a HomeCmp and Shared Service.

Look at the shared service's constructor. I have manually set 'Guest' string and trying to emit UserModel object. But it doesn't receive object in HomeCmp's ngOnInit.

If you click the button, it will work. any suggestion?

How can I show Guest string when I run the app through EventEmitter.

service.ts

import {EventEmitter} from 'angular2/core';
import {UserModel} from 'app/models';
export class NavService {

  user:EventEmitter<UserModel>=new EventEmitter();
  constructor() {
    console.log('constructor')

    userDetail=new UserModel();
    userDetail.name="guest";
    userDetail.loggedIn=false;
    console.log(userDetail);
    this.user.emit(userDetail);
  }

  ngOnInit(){ // just wanted to check if it could help or not. I know it belongs to Component's life cycle.
    console.log('onit')
  }

   setUserDetail(str)
  {
    console.log('SetUserDetail started');
    userDetail.name=str;
    userDetail.loggedIn=true;
    this.user.emit(userDetail);
  }

  getUserDetail()
  {
    return this.user;
  }
}

Homecmp.ts

import {Component} from 'angular2/core';
import {NavService} from '../services/NavService';
import {UserModel} from 'app/models';

@Component({
  selector: 'my-app',
  template: `<div>User object:</div>

  {{userData|json}}
  <button (click)="setuser()">Click</button>
  `
})
export class HomeCmp {
  constructor(authService:NavService){
        this.authService=authService; 

    }
  setuser()
  {
   this.authService.setUserDetail("micronyks");
  }


     ngOnInit(){
                console.log('here is userInfo');
                this.subscription = this.authService.getUserDetail()
                                    .subscribe((item) => {this.userData=item;
                                                          console.log('Finally i m working');
                                                          console.log(this.userInfo);

                                                         });
     }

    ngOnDestroy() {

    }
}

models.ts

export class UserModel()
{
 private name:string;
 private loggedIn:boolean=false;
}

working Demo

回答1:

Angular creates a NavService instance and while doing this, the constructor is executed and the event fired. As next step Angular creates an instance of the HomeCmp component and passes the NavService in. Then in HomeCmps constructor a listener for user:EventEmitter is registered. After this registration no event is emitted and therefore not recieved anymore.

What you want to do is to delay firing the event. I assume your situation is only for testing purposes and in practice firing an event in the constructor isn't necessary anyway.

For testing purposes you can just wrap this.user.emit(userDetail); in a setTimeOut

setTimeOut(() => this.user.emit(userDetail), 1);

Answer

来源：https://stackoverflow.com/questions/35500890/eventemitter-in-shared-services-constructor-doenst-emit-data

标签

angular

eventemitter