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我是Angular2的新手,我有以下服务文件,它给了我一个错误。无法使用时间间隔从数组返回一个Observable
import { Injectable } from '@angular/core';
import { Http, Response } from '@angular/http';
import { Observable} from 'rxjs/Observable';
import 'rxjs/add/operator/map';
import 'rxjs/add/operator/catch';
import 'rxjs/add/observable/throw';
import 'rxjs/add/observable/from';
import 'rxjs/add/observable/interval';
import 'rxjs/add/operator/take';
@Injectable()
export class UserService {
constructor(private _http: Http) { }
private getUserUrl = 'data/data.json';
private users = [
{ personal: { name: 'Saurabh', age: 24 }, role: 'Web Developer', hobby: 'Coding' },
{ personal: { name: 'Sunil', age: 24 }, role: 'Manual Tester', hobby: 'Drinking tea' },
{ personal: { name: 'Digvijay', age: 24 }, role: 'Onsite Tester', hobby: 'Gaming' },
{ personal: { name: 'Vinod', age: 24 }, role: 'C# Developer', hobby: 'Flirting' }
];
getUsers() {
return Observable.from(this.users) //tried with and without this `.from
.interval(2000)
.take(this.users.length) // end the observable after it pulses N times
.map(function (i) { return this.users[i]; });
}
addUser(user: any) {
this.users.push(user);
}
_errorHandler(error: Response) {
return Observable.throw(error || "Server error");
}
}
我的期望是,上面的代码应该一次发出一个用户。我可以在我的组件中订阅该用户,并产生一个懒惰的用户加载效果。我的部分代码是:
export class UserComponent implements OnInit {
users :any = [];
constructor(private _userService: UserService, private _router : Router) { }
ngOnInit() {
//this.users = this._userService.getUsers();
//code for real http data : Observable do not send data unless you subscribe to them
this._userService.getUsers().subscribe(response => this.users.push(response));
}
}
我终于在迭代使用DOM这*ngFor
名单。
但让我吃惊的可观测找不到阵列本身和.map
给出一个错误:
TypeError: Cannot read property '0' of undefined
at MapSubscriber.eval [as project] (http://localhost:8080/app/services/user.service.js:41:50)
如果我只是从我的服务回报用户阵列,它工作正常。所以我在这里做什么?
作为事实上,我已认识到这一点,并改变了我的代码为'.MAP(第(i)=> this.users [I]);'我没有很多用过的箭头函数,但我认为这应该起作用。单行'return'不需要用大括号包裹。但是,这给了我错误,你的代码工作正常。我的语法错了吗? –
我在答案中指定的两种语法都是等价的。如果给出.map((i)=> this this.users [i]),它将被视为'.map((i)=> {return return this.users [i];})'CHeck [here](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Functions/Arrow_functions)。 –