Angular2 HTTP GET - Cast response into full object

问题:

I have this simple Component

import {Component} from 'angular2/core';
import {RouterLink, RouteParams} from 'angular2/router';
import {Http, Response, Headers} from 'angular2/http';
import {User} from '../../models/user';
import 'rxjs/add/operator/map';


@Component({
    template: `
        <h1>{{user.name}} {{user.surname}}</h1>
    `,
    directives: [RouterLink],
})
export class UserComponent {

    user: User;

    constructor(private routeParams: RouteParams,
        public http: Http) {
            this.user = new User();
            this.http.get('http://localhost:3000/user/' + this.routeParams.get('id'))
                .map((res: Response) => res.json())
                .subscribe((user: User) => this.user = user);
        console.log(this.user);
    }
}

Why does subscribe not cast the response into a full User object. When I am logging the user variable my console say User {_id: undefined, name: undefined, surname: undefined, email: undefined}. But nevertheless binding to .name and .surname in the view is working..

What happens here? Where is the user actually stored?

回答1:

Found a solution here: https://stackoverflow.com/a/29759472/2854890

My Method now looks like this:

constructor(private routeParams: RouteParams,
    public http: Http) {
    this.user = new User();
    this.http.get('http://localhost:3000/user/' + this.routeParams.get('id'))
        .map((res: Response) => res.json())
        .subscribe((json: Object) => {
            this.user = new User().fromJSON(json);
        });
}

I enhanced the Serializable by returning the object in the end, so I can leave out something like

var u = new User();
u.fromJSON(...);

and just write

new User().fromJSON(json);

Serializable class

export class Serializable {

    fromJSON(json) {
        for (var propName in json)
            this[propName] = json[propName];
        return this;
    }

}

回答2:

Good practice is to consume data from GET response using

Observable<Model>

(regarding to Angular documentation https://angular.io/guide/http) so...

// imports

import {HttpClient} from "@angular/common/http";

// in constructor parameter list

private http: HttpClient

// service method

getUser(): Observable<User> {return this.http.get<User>({url}, {options});}

You do not need to do anything more. I consider this approach as most friendly.

回答3:

That's not supported by TypeScript.

See How do I cast a JSON object to a typescript class for more details.