How to get data from observable in angular2

问题

I am trying to print the result of http call in Angular using rxjs

Consider the following code

import { Component, Injectable, OnInit } from '@angular/core';
import { Http, HTTP_PROVIDERS } from '@angular/http';
import 'rxjs/Rx';

@Injectable()
class myHTTPService {
  constructor(private http: Http) {}

  configEndPoint: string = '/my_url/get_config';

  getConfig() {

    return this.http
      .get(this.configEndPoint)
      .map(res => res.json());
  }
}

@Component({
    selector: 'my-app',
    templateUrl: './myTemplate',
    providers: [HTTP_PROVIDERS, myHTTPService],


})
export class AppComponent implements OnInit {

    constructor(private myService: myHTTPService) { }

    ngOnInit() {
      console.log(this.myService.getConfig());
    }
}

Whenever I tried to print out the result of getconfig it always return

Observable {_isScalar: false, source: Observable, operator: MapOperator}

even though I return a json object instead.

How would I print out the result of getConfig ?

回答1:

You need to subscribe to the observable and pass a callback that processes emitted values

this.myService.getConfig().subscribe(val => console.log(val));

回答2:

Angular is based on observable instead of promise base as of angularjs 1.x, so when we try to get data using http it returns observable instead of promise, like you did

 return this.http
      .get(this.configEndPoint)
      .map(res => res.json());

then to get data and show on view we have to convert it into desired form using RxJs functions like .map() function and .subscribe()

.map() is used to convert the observable (received from http request)to any form like .json(), .text() as stated in Angular's official website,

.subscribe() is used to subscribe those observable response and ton put into some variable so from which we display it into the view

this.myService.getConfig().subscribe(res => {
   console.log(res);
   this.data = res;
});

回答3:

this.myService.getConfig().subscribe(
  (res) => console.log(res),
  (err) => console.log(err),
  () => console.log('done!')
);

来源：https://stackoverflow.com/questions/36395252/how-to-get-data-from-observable-in-angular2

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typescript

angular

reactive-programming

rxjs

observable