錯誤的構造

Question

我有這樣的服務：

import {Injectable} from 'angular2/core'; 
import {Http, Headers} from 'angular2/http'; 
import 'rxjs/Rx'; 

@Injectable() 

export class DataService() { 

    constructor(private _http: Http) {} 


} 

這是引發此錯誤：

Error: Zone</Zone.prototype.run@http://localhost:3000/node_modules/angular2/bundles/angular2-polyfills.js:1243:21 
    zoneBoundFn@http://localhost:3000/node_modules/angular2/bundles/angular2-polyfills.js:1220:21 
    lib$es6$promise$$internal$$tryCatch@http://localhost:3000/node_modules/angular2/bundles/angular2-polyfills.js:468:17 
    lib$es6$promise$$internal$$invokeCallback@http://localhost:3000/node_modules/angular2/bundles/angular2-polyfills.js:480:18 
    lib$es6$promise$$internal$$publish@http://localhost:3000/node_modules/angular2/bundles/angular2-polyfills.js:451:12 
    @http://localhost:3000/node_modules/angular2/bundles/angular2-polyfills.js:123:10 
    Zone</Zone.prototype.run@http://localhost:3000/node_modules/angular2/bundles/angular2-polyfills.js:1243:21 
    zoneBoundFn@http://localhost:3000/node_modules/angular2/bundles/angular2-polyfills.js:1220:21 
    lib$es6$promise$asap$$flush@http://localhost:3000/node_modules/angular2/bundles/angular2-polyfills.js:262:10 

    Evaluating http://localhost:3000/app/data.service.js 
    Error loading http://localhost:3000/app/data.service.js as "./data.service" from http://localhost:3000/app/app.component.js 
addToError() 

任何想法，爲什麼？

Answer 1

你應該在類名之後刪除括號：

@Injectable() 
export class DataService { // <----------- 

，而不是

@Injectable() 
export class DataService() { // <-----------