如何将JSON数据加载到Angular2组件中 [英] How to I load JSON data into Angular2 component
问题描述
在tinterweb上浏览了许多教程之后，我终于开始尝试使用Angular2构建对我有用的东西，并且遇到了我的第一个问题.我似乎无法将JSON数据加载到服务组件中.
After running through many tutorials on tinterweb I have finally started to try and build something useful to me using Angular2 and I have come across my first issue. I cannot seem to load JSON data into my service component.
我的people.json文件存储在顶部文件夹中名为data的文件夹中.
my people.json file is stored in a folder called data in the top folder.
people.json
people.json
"people":[
{ age: 40, name: "Jordan Houston" },
{ age: 38, name: "Robert Eastham" },
{ age: 23, name: "Josh Beh" },
{ age: 23, name: "Joseph Canina" },
{ age: 24, name: "Alexandra Wilkins" },
{ age: 22, name: "Kiersten Costanzo" },
{ age: 23, name: "Ku Sherwood" },
{ age: 25, name: "Arta Halili" },
{ age: 24, name: "Patrick Cooney" },
{ age: 23, name: "Z.A. Perr" },
{ age: 18, name: "Tyler Mulligan" },
{ age: 26, name: "Dennis Dempsey" },
{ age: 32, name: "Francis Yeager" },
{ age: 23, name: "Phil Belardi" }
]
我相信我的问题出在friends.service.ts
I believe my issue lies in the friends.service.ts
friend.service.ts
friend.service.ts
import {Injectable} from 'angular2/core';
import {Http, HTTP_PROVIDERS} from 'angular2/http';
@Injectable()
export class FriendService {
friends:Array<any>;
constructor(private http:Http)
{
//console.log(">>friend.service.ts:constructor--")
http.request('./data/people.json')
.subscribe(response => this.friends = response.json()));
}
getFriends()
{
//console.log(">>friend.service.ts:getFriends--")
console.log(this.friends)
return this.friends
}
}
friend.service.ts用于friend.component.ts
friend.service.ts is used within the friend.component.ts
friend.component.ts
friend.component.ts
import { Component } from 'angular2/core';
import { FriendService } from 'app/friend.service';
@Component({
selector: 'my-friends',
providers: [FriendService],
styles: [`
div {
background-color:#EFEFEF;
margin-bottom:15px;
padding:15px;
border:1px solid #DDD;
box-shadow:2px 2px 2px 0 rgba(0, 0, 0, 0.3);
border-radius:3px;
}
h2 {
text-align: center;
}
`],
template: `
<h1>Hello from the {{ componentName }}!</h1>
<div *ngFor="#f of friends">
<h3>Name: {{ f.name }}</h3>
<h4>Age: {{ f.age }}</h4>
</div>
`
})
export class FriendComponent {
componentName: 'FriendComponent';
constructor(private _friendService: FriendService)
{
this.friends = _friendService.getFriends();
}
}
它存在于main.ts中
this lives within main.ts
main.ts
import { Component } from 'angular2/core';
import { bootstrap } from 'angular2/platform/browser';
import { FriendComponent } from 'app/friend.component';
import {HTTP_PROVIDERS} from 'angular2/http';
@Component({
selector: 'my-app',
directives: [FriendComponent],
styles: [`
h1 {
color:#545454;
background:#02A8F4;
padding:15px;
box-shadow:2px 2px 2px 0 rgba(0, 0, 0, 0.3);
}
`]
template: `
<div>
<h1>Hello from the {{componentName}}.</h1>
<my-friends></my-friends>
</div>
`
})
export class AppComponent {
componentName: 'AppComponent'
}
bootstrap(AppComponent,[HTTP_PROVIDERS])
...这是索引页...
...and here is the index page...
<!DOCTYPE html>
<html>
<head>
<script>document.write('<base href="' + document.location + '" />');</script>
<meta name="viewport" content="width=device-width, initial-scale=1.0">
<!--Add Bootstrap CSS Styles-->
<link rel="stylesheet" href="https://maxcdn.bootstrapcdn.com/bootstrap/3.3.6/css/bootstrap.min.css">
<!-- IE required polyfills, in this exact order -->
<script src="https://cdnjs.cloudflare.com/ajax/libs/es6-shim/0.34.1/es6-shim.js"></script>
<script src="https://cdnjs.cloudflare.com/ajax/libs/systemjs/0.19.20/system-polyfills.js"></script>
<script src="https://npmcdn.com/angular2/es6/dev/src/testing/shims_for_IE.js"></script>
<!-- Angular polyfill required everywhere -->
<script src="https://code.angularjs.org/2.0.0-beta.8/angular2-polyfills.js"></script>
<script src="https://code.angularjs.org/tools/system.js"></script>
<script src="https://code.angularjs.org/tools/typescript.js"></script>
<script src="https://code.angularjs.org/2.0.0-beta.8/Rx.js"></script>
<script src="https://code.angularjs.org/2.0.0-beta.8/angular2.dev.js"></script>
<script src="https://code.angularjs.org/2.0.0-beta.8/router.dev.js"></script>
<script src="https://code.angularjs.org/2.0.0-beta.8/http.dev.js"></script>
<script>
System.config({
transpiler: 'typescript',
typescriptOptions: { emitDecoratorMetadata: true },
packages: {
'api': {defaultExtension: 'ts'},
'app': {defaultExtension: 'ts'}
}
});
System.import('app/main')
.then(null, console.error.bind(console));
</script>
</head>
<body class="container">
<my-app>Loading...</my-app>
</body>
</html>
任何帮助将不胜感激;)
Any help would be greatly appreciated ;)
推荐答案
实际上，这是因为您的数据是异步加载的.因此，在组件的构造函数中，最初会得到一个未定义的值.
In fact, it's because your data are loaded asynchronously. So within the constructor of your component, you initially get an undefined value.
constructor(private _friendService: FriendService) {
this.friends = _friendService.getFriends();
}
要使构造函数保持这种状态，您需要重构代码以使服务的getFriends方法返回可观察的结果:
To keep your constructor like that, you need to refactor your code to make the getFriends method of your service return an observable:
@Injectable()
export class FriendService {
constructor(private http:Http) {
}
getFriends() {
return this.http.request('./data/people.json')
.map(res => res.json());
}
}
然后，您可以使用async管道进入组件模板:
Then you can use the async pipe into your component template:
template: `
<h1>Hello from the {{ componentName }}!</h1>
<div *ngFor="#f of friends | async">
<h3>Name: {{ f.name }}</h3>
<h4>Age: {{ f.age }}</h4>
</div>
`
这篇关于如何将JSON数据加载到Angular2组件中的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！
