处理 Angular 2 中的奇怪问题。
如果您查看下面的组件，该服务会返回一个已解析的对象——例如我可以console.log。您可以看到粘贴为注释的输出。每当我尝试在视图中使用所述对象时，都会出现错误：EXCEPTION: TypeError: Cannot read property 'subject' of undefined in [{{theData.subject}} in SubjectHomeComponent@2:27].
这对我来说没有意义，因为我可以在控制台中看到对象就好了。运行typeof还返回它是一个对象。
组件代码
import { Component, View } from 'angular2/core'
import { CORE_DIRECTIVES } from 'angular2/common'
import {SubjectService} from "../../services/subject/SubjectService.ts";
import Rx from 'rxjs/Rx'
import { Response } from 'angular2/http'
import {ROUTER_PROVIDERS} from "angular2/router";
import {RouteParams} from "angular2/router";
@Component({
selector: 'subjectHomeComponent',
providers: [SubjectService]
})
@View({
template: `
Hello World <span>{{theData.subject}}</span>
`
})
export class SubjectHomeComponent{
constructor(subjectService: SubjectService, params: RouteParams){
this.id = params.get('id')
subjectService.getSubjectCardsAndNotes(this.id)
.subscribe((res: Response) => {
this.theData = res
console.log(res) //returns {"subject":{"id":1,"name":"Spanish","created_at":"2016-01-23T06:54:50.321Z","updated_at":"2016-01-23T06:54:50.321Z"},"subject_id":1,"notes":[{"id":1,"title":"first note","body":"here i am!","created_at":"2016-01-27T03:10:09.238Z","updated_at":"2016-01-27T03:10:09.238Z","subject_id":1},{"id":2,"title":"first_note","body":"hello _buddy_","created_at":"2016-01-28T20:45:36.044Z","updated_at":"2016-01-28T20:45:36.044Z","subject_id":1}]}
});
}
}
服务代码（我认为不相关，但你永远不知道）
import {Injectable} from "angular2/core";
import {Http, HTTP_PROVIDERS, Response} from "angular2/http";
import Rx from 'rxjs/Rx'
import 'rxjs/add/operator/map';
@Injectable()
export class SubjectService{
constructor(public http: Http){
}
getSubject(){
return this.http.request('/subjects.json')
.map((response) => response.json())
}
getSubjectCardsAndNotes(id){
return this.http.request(`subjects/${id}/subject_cards_and_notes.json`)
.map((response) => response.json())
}
}