Angular2 Http Undefined error

Question

I am trying to make a get request using the Http module in Angular2 (angular 2.0.0-beta.0 and typescript 1.7.5), but I have some kind of synchronise problem. I put everything in one .ts file to make it easier to communicate.

Everything compiles fine in typescript but Chrome shows the following error the in console :

EXCEPTION: TypeError: Cannot read property '_id' of undefined in [Id: {{contact._id}} Name: {{contact.name}} in Test@1:13]
ORIGINAL EXCEPTION: TypeError: Cannot read property '_id' of undefined
ORIGINAL STACKTRACE:
TypeError: Cannot read property '_id' of undefined
...
...
Object {_id: "5695e53d98ff94671ae22d55", name: "Piet Pannenkoek", email: "piet@gmail.com", number: "435345"}

test1.ts:

import {bootstrap} from 'angular2/platform/browser';
import {Component} from 'angular2/core';
import {Http, Response, HTTP_PROVIDERS} from 'angular2/http';
import 'rxjs/Rx';

@Component({
    selector: 'my-app',
    template: `
        <div>Id: {{contact._id}} Name: {{contact.name}}</div>
    `,
    providers: [HTTP_PROVIDERS]
})

export class Test {

    public contact: Contact;

    constructor(private http: Http) {}

    ngAfterViewInit() {
        this.http.get('/api/contactlist/5695e53d98ff94671ae22d55')
            .map((res: Response) => res.json())
            .subscribe(res => {
                console.log(res);
                this.contact = res;
            });
    }
}

export class Contact {
    constructor (public _id: string, public name: string, public email: string, public number: string) {};
}

bootstrap(Test);

http://localhost:3000/api/contactlist/5695e53d98ff94671ae22d55

{"_id":"5695e53d98ff94671ae22d55","name":"Piet Pannenkoek","email":"piet@gmail.com","number":"435345"}

Strange is that another (little different) version test2.ts doesn't give any errors:

import {bootstrap} from 'angular2/platform/browser';
import {Component} from 'angular2/core';
import {Http, Response, HTTP_PROVIDERS} from 'angular2/http';
import 'rxjs/Rx';

@Component({
    selector: 'my-app',
    template: '<div *ngFor="#contact of contacts">Id: {{contact._id}} Name: {{contact.name}}</div>',
    providers: [HTTP_PROVIDERS]
})

export class Test {

    public contacts: Contact[] = [];

    constructor(private http: Http) {}

    ngAfterViewInit() {
        this.http.get('/api/contactlist')
            .map((res: Response) => res.json())
            .subscribe(res => {
                console.log(res);
                this.contacts = res;
            });
    }
}

export class Contact {
    constructor (public _id: string, public name: string, public email: string, public number: string) {};
}

bootstrap(Test);

http://localhost:3000/api/contactlist

[{"_id":"5695e53d98ff94671ae22d55","name":"Piet Pannenkoek","email":"piet@gmail.com","number":"435345"},{"_id":"56a63059b2cb5f4b10efaf9a","name":"Jan Janssen","email":"jan@email.com","number":"642"},{"_id":"56a6307bb2cb5f4b10efaf9b","name":"Gerard de Boer","email":"gerard@email.com","number":"1234"},{"_id":"56abe853211b52a441f6c45f","name":"Bjorn Borg","email":"bjorn@borg.com","number":"123"},{"_id":"56abe8da211b52a441f6c460","name":"Hans Dobbelsteen","email":"hans@email.com","number":"752"},{"_id":"56abe8fe211b52a441f6c461","name":"Marco van Basten","email":"marco@email.com","number":"961"}]

Answer 1

You are trying to use contact object before it's resolved. Either use elvis-operator {{ contact?._id }} or show block conditionally:

template: `
    <div *ngIf="contact">Id: {{contact._id}} Name: {{contact.name}}</div>
`,

Answer 2

you are trying to access contact object whihc is undefined/null till the template load ie your object has not loaded properly at the time of template load. so to avoid this you have to use elvis operator like following

{{contact?._id}} and {{contact?.name}}

by using elvis operator angualr will not throw any error if your contact object has no value named name or id . whenever your binding load properly to contact Object angular will reflact changes to template.

try this one surely work for you.

<div>Id: {{contact?._id}} Name: {{contact?.name}}</div>

Answer 3

Angular tries to bind before the data arrived.

<div>Id: {{contact?._id}} Name: {{contact?.name}}</div>

should work.