从angular 2服务返回http响应

Question

I have the following code for my service

import {Injectable} from 'angular2/core';
import {Http} from 'angular2/http';
import {Response} from "angular2/http";
import {PRIVATE_SERVERS} from "../mock/private_servers_list";
import 'rxjs/Rx';
/*import {PRIVATE_SERVERS} from "../mock/private_servers_list";*/

@Injectable()
export class PrivateServerService {
    http= null;
    PRIVATE_SERVERS = null;

    constructor(http:Http){
        this.http = http;
    }

    logError(err){
        console.log("some error");
    }

    getPrivateServers(){
        this.http.get('http://private-server.eviry.com/get_private_servers')
            .map(res => res.json())
            .subscribe(
                data => this.PRIVATE_SERVERS = data, //printing data here gives me the correct value
                err => this.logError(err),
                () => console.log('Private Server fetching complete')
            );

        console.log(this.PRIVATE_SERVERS);
        return this.PRIVATE_SERVERS;

    }
}

I have injected this service in to a component called private-server.component. Basically, in this service I am trying to get a list of private servers using the url http://private-server.eviry.com/get_private_servers

I access this url in getPrivateServers() function. When I print the response within the subscribe method, I can see the data fetched correctly.

However, when I try to console.log(this.PRIVATE_SERVERS) , it prints null. Is this the correct way to use the angular service or is there a way to make it wait for the response?

Answer 1

The assignment happens in an asynchronous callback. If you want to use its value outside that callback, you need to wait for it to complete.

Answer 2

You can also use Event Emitter to react asynchronous to the response. Here is an good introduction to Observables in Angular2.

Answer 3

PrivateServerService.ts

import { Injectable } from 'angular2/core';
import { Http } from 'angular2/http';
import { Response } from "angular2/http";
import { PRIVATE_SERVERS } from "../mock/private_servers_list";
import 'rxjs/Rx';
/*import {PRIVATE_SERVERS} from "../mock/private_servers_list";*/

@Injectable()
export class PrivateServerService {
    PRIVATE_SERVERS = null;

    constructor(private http: Http) {
        this.setPrivateServerMocksData();
    }

    logError(err) {
        console.log("some error");
    }

    getPrivateServers() {
        return this.http.get('http://private-server.eviry.com/get_private_servers')
            .map(res => res.json());
    }

    setPrivateServerMocksData() {
        this.getPrivateServers()
            .subscribe((data) => {
                this.PRIVATE_SERVERS = data
                console.log(this.PRIVATE_SERVERS);
            },
            (err) => {
                this.logError(err)
            });
    }

}

YourComponent.ts

 getPrivateServerInfo() {
                this.privateServerService.getPrivateServers()
                    .subscribe((data) => {
                        //you have your data here to work with
                        console.log(data);
                    },
                    (err) => {
                        this.logError(err)
                    });
            }