angular2 routing - Angular 2.0 BETA - HTTP Request and displaying its attributes -


we having issues displaying fetched data mapped interface. there these 3 files called:

  • teacher.service.ts
  • teacher.component.ts
  • teacher.ts

we fetched normal javascript object can't figure out how display in template. tried display {{teacher.firstname}} -> failed , {{test.firstname}} -> succeeded. test javascript object made hand , has same properties(firstname, lastname) interface has.

here test-results + error-messages:

enter image description here

here code:

// teacher.ts   export interface teacher {     id: number,     firstname: string,     lastname: string,     schools: string[],     created_at: string,     updated_at: string } 
// teacher.service.ts  import {injectable} 'angular2/core'; import {http, headers, request, requestoptions, requestmethod} 'angular2/http'; import {observable} 'rxjs/observable'; import {teacher} '../interfaces/teacher';  @injectable() export class teacherservice {      public constructor(private http:http) {     }      public searchteacher(name:string) {         if (name.length >= 2) {             return this.http.get('http://localhost/xxxx/teacher/search/' + name).map(res => res.json());         } else {             return false;         }     }      public getteacher(id:string) {         return this.http.get('http://localhost/xxxx/teacher/' + id)             .map(res => <teacher> res.json());     }  } 
// teacher.component.ts  import {component, oninit} 'angular2/core';  import {router, routeparams} 'angular2/router'; import {teacherservice} '../services/teacher.service'; import {teacher} '../interfaces/teacher'; import {form_directives} 'angular2/common';  @component({     template: '<h1>{{teacher.firstname}}</h1>' +    // can use {{t.firstname}} can't use {{teacher.firstname}}     '<input type="button" (click)="log()">',     providers: [teacherservice],     directives: [form_directives] }) export class teachercomponent implements oninit{     public teacher : teacher;     public name : string;      public test = {firstname: "horst", lastname: "peter"}; // test object equals normal json-object      constructor(private _routeparams:routeparams, private _teacherservice:teacherservice) {}      ngoninit(){         let id = this._routeparams.get('id');         return this._teacherservice.getteacher(id).subscribe( // fetch things server             data => this.teacher = data,             err => alert(err));     }      private log(){  // log function simple click event         console.log(this.teacher);         console.log(this.test);     } }

you assigning value test property synchronously, assigning value teacher asynchrounously. first time angular tries access firstname property of teacher, teacher still undefined, that's why error 1 not other. following solutions this:

1- use elvis operator @eric mentioned:

template: '<h1>{{teacher?.firstname}}</h1>'

2- arguably better, don't try render component until have value teacher:

template: '<h1 *ngif="teacher">{{teacher.firstname}}</h1>'


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