Angular学习系列八：调用服务方法

 1 import { Injectable } from ‘@angular/core‘;
 2 import { Observable } from ‘rxjs‘;
 3 @Injectable({
 4   providedIn: ‘root‘
 5 })
 6 export class RequestService {
 7 
 8   constructor() { }
 9 
10   //同步方式
11   getData() {
12     alert("我是服务方法");
13   }
14 
15   //回调方式
16   getCallbackData(cb) {
17     setTimeout(() => {
18 
19       var username = ‘xiao ming--callback‘;
20       // return data;
21       cb(username);
22     }, 1000);
23   }
24 
25   //promise
26   getPromiseData(){
27 
28     return new Promise((resolve,reject)=>{
29 
30       setTimeout(() => {
31         var username = ‘xiao ming--promise‘;
32         resolve(username);
33       }, 1000);
34     });
35   }
36 
37   //rxjs
38   getRxjsData(){
39 
40     return new Observable((obj)=>{
41 
42       setTimeout(() => {
43         var username="xiao hong -- rxjs";
44         obj.next(username);
45       }, 3000);
46 
47     });
48   } 
49 }

 1 import { Component, OnInit} from ‘@angular/core‘;
 2 import { RequestService } from ‘../../services/request.service‘;
 3 @Component({
 4   selector: ‘app-home‘,
 5   templateUrl: ‘./home.component.html‘,
 6   styleUrls: [‘./home.component.css‘]
 7 })
 8 export class HomeComponent implements OnInit {
 9  
10   constructor(public req: RequestService) { }
11 
12   ngOnInit() {
13   }
14   
15   getServiceMethod() {
16     this.req.getData();
17   }
18 
19 
20   //回调 获取异步数据
21   getAsyncMethod() {
22     this.req.getCallbackData((uname) => {
23       alert(uname);
24     })
25   }
26 
27   //promise获取异步数据
28   getPromiseMethod() {
29     var pro = this.req.getPromiseData();
30     pro.then((data) => {
31       alert(data);
32     });
33   }
34 
35   //rxjs获取异步数据
36   getRxjsMethod() {
37 
38     var rxjsdata = this.req.getRxjsData();
39     var start = rxjsdata.subscribe((data) => {
40       alert(data);
41     });
42 
43    
44   }
45 
46 
47   removeRxjsMethod() {
48 
49     var rxjsdata = this.req.getRxjsData();
50     var start = rxjsdata.subscribe((data) => {
51       alert(data);
52     });
53 
54     setTimeout(() => {
55       start.unsubscribe();//取消订阅：由于上面方法执行3s中，在1s后，就取消了该请求
56     }, 1000);
57   }
58 
59 }

 1 <button (click)="getServiceMethod()">我可以调用服务里面的方法哦（同步）</button>
 2 <br>
 3 
 4 <button (click)="getAsyncMethod()">我可以调用服务里面的方法哦（异步-callback)</button>
 5 <br>
 6 
 7 <button (click)="getPromiseMethod()">我可以调用服务里面的方法哦（异步-promise）</button>
 8 <br>
 9 <button (click)="getRxjsMethod()">我可以调用服务里面的方法哦（异步-rxjs）</button>
10 <br>
11 <button (click)="getRxjsMethod()">我可以调用服务里面的方法哦（rxjs,取消订阅）</button>
12 <p>home works!</p>
13 <hr>