怎么在angular2中实现一个Http请求？相信很多没有经验的人对此束手无策，为此本文总结了问题出现的原因和解决方法，通过这篇文章希望你能解决这个问题。
提供HTTP服务
HttpModule并不是Angular的核心模块。 它是Angular用来进行Web访问的一种可选方式，并位于一个名叫@angular/http的独立附属模块中.
编辑app.module.ts
import { HttpModule, JsonpModule } from '@angular/http';
@NgModule({
imports: [
HttpModule,
JsonpModule
],
})angular-in-memory-web-api
npm install angular-in-memory-web-api --save-dev
This in-memory web api service processes an HTTP request and returns an Observable of HTTP Response object in the manner of a RESTy web api.
:base/:collectionName/:id? GET api/heroes // all heroes GET api/heroes/42 // the character with id=42 GET api/heroes?name=^j // 'j' is a regex; returns heroes whose name starting with 'j' or 'J' GET api/heroes.json/42 // ignores the ".json"
之前测试时用的app/mock/user_data_memory_mock.ts数据
import {User} from '../model/User';
import { InMemoryDbService } from 'angular-in-memory-web-api';
export class UserDataMemoryMock implements InMemoryDbService{
createDb() {
const users: User[] = [
new User('chenjianhua_a', 21, '2290910211@qq.com', '123456'),
new User('chenjianhua_b', 22, '2290910211@qq.com', '123456'),
new User('chenjianhua_c', 23, '2290910211@qq.com', '123456'),
new User('chenjianhua_d', 24, '2290910211@qq.com', '123456'),
new User('chenjianhua_e', 25, '2290910211@qq.com', '123456'),
new User('chenjianhua_f', 26, '2290910211@qq.com', '123456'),
];
return {users};
}
}编辑app.module.ts
import { InMemoryWebApiModule } from 'angular-in-memory-web-api';
import { UserDataMemoryMock } from './mock/user_data_memory_mock';
@NgModule({
imports: [
InMemoryWebApiModule.forRoot(UserDataMemoryMock),
]
})导入InMemoryWebApiModule并将其加入到模块的imports数组。 InMemoryWebApiModule将Http客户端模拟的后端服务forRoot()配置方法需要UserMemoryMockService类实例，用来向内存数据库填充数据
编辑app/service/user.restful.service.ts
import {Injectable} from '@angular/core';
import { Headers, Http } from '@angular/http';
import 'rxjs/add/operator/toPromise';
import { User } from '../model/User';
import { Logger } from './logger.service';
@Injectable()
export class UserService {
private USERURL = 'api/users';
private headers = new Headers({'Content-Type': 'application/json'});
constructor(private Log: Logger,
private http: Http) { }
getUserByName(name: string): Promise {
const url = `${this.USERURL}/?name=${name}`;
return this.http.get(url)
.toPromise()
.then(response => response.json().data as User)
.catch(this.handleError);
}
getUsers(): Promise {
console.log('Get User!');
return this.http.get(this.USERURL)
.toPromise()
.then(response => response.json().data as User[])
.catch(this.handleError);
}
create(name: string): Promise {
return this.http
.post(this.USERURL, JSON.stringify({name: name}), {headers: this.headers})
.toPromise()
.then(res => res.json().data as User)
.catch(this.handleError);
}
private handleError(error: any): Promise{
console.log('An error occurred :', error);
return Promise.reject(error.message);
}
} 编辑app/components/app-loginform/app.loginform.ts
import { Component, OnInit } from '@angular/core';
import { Logger } from '../../service/logger.service';
import { UserService } from '../../service/user.restful.service';
import { User } from '../../model/User';
import { Subject } from 'rxjs/Subject';
@Component({
selector: 'app-loginform',
templateUrl: './app.loginform.html',
styleUrls: ['./app.loginform.css'],
providers: [
Logger,
UserService
]
})
export class AppLoginFormComponent implements OnInit {
users: User[];
submitted = false;
model = new User('1', 'fangfang', 22, '2290910211@qq.com', '123456');
constructor(
private Log: Logger,
private userService: UserService
){}
ngOnInit(): void{
this.userService
.getUsers()
.then( users => this.users = users);
}
onSubmit(): void {
this.userService.getUserByName(this.model.name)
.then( user => {
console.log('user.name', user[0].name);
console.log('user.password', user[0].password);
if(user[0].name === this.model.name
&& user[0].password === this.model.password){
this.Log.log('login success!');
this.submitted = true;
}else{
this.Log.log('login failed!');
this.submitted = false;
}
})
.catch(errorMsg => console.log(errorMsg));
}
}HTTP Promise
Angular 的http.get返回一个 RxJS 的Observable对象。 Observable是一个管理异步数据流的强力方式。
现在，我们先利用toPromise方法把Observable直接转换成Promise对象
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