How to map an angular 2 class from an http call - json

Question

I'm new in Angular.
I've a class called User:
export class User {
private id: number;
private name: string;
private surname: string;
get Id(): number {
return this.id;
}
set Id(newId: number) {
this.id = newId;
}
get Name(): string {
return this.name;
}
set Name(newName: string) {
this.name = newName;
}
get Surname(): string {
return this.surname;
}
set Surname(newSurname: string) {
this.surname = newSurname;
}
}
...a function to retrive an array of user:
getValues() {
this.usersService.getUsers()
.subscribe((users: User[]) => this.dataSource = users);
}
and a method to retrive the users array from backend WebApi:
getUsers(): Observable<User[]> {
return this.http.get<User[]>(this.usersSearchUrl)
.pipe(
tap(users => this.log(`fetched users`)),
catchError(this.handleError('getUsers', []))
);
}
finally the json returned from the webapi:
[{"id":"1","name":"Alberico","surname":"Gauss"},{"id":"2","name":"Anassimandro","surname":"Dirac"},{"id":"3","name":"Antongiulio","surname":"Poisson"}]
I would have expected that the call would automatically mapped the User class, instead it only gives me an array of type User, in fact if I write something in my component .subscribe((utenti: Utente[]) => console.log(utenti[0].Surname)); the console writes me "undefined". Can you tell me where I'm wrong? Thanks

Answer 1

You are retrieving JSON from your backend, as is expected. A Javascript (or typescript) class is not the same thing.
When the JSON is returned, it can be automatically converted into a simple JSON object in Javascript but it will NOT include all your getters and setters. So these class methods are not available, which is why you get undefined.
Remove all the getters and setters and add a constructor. Then you can just call Surname directly as a property and it will return the value (since it will then just be a plain JSON object).
export class User {
constructor() {
}
public id: number;
public name: string;
public surname: string;
}
Or without a constructor, and just declare the properties directly:
export class User {
public id: number;
public name: string;
public surname: string;
}
Or you could also use an interface:
export interface User {
id: number;
name: string;
surname: string;
}
You can read more about this issue here and here.

Answer 2

I think in component ts use like this code:
users: User[];
constructor(
private us: usersService,
public auths: AuthService
)
this.us.getUsers.subscribe(
users=> {
this.users= users.map((user) => {
return new User(user);
});
}
);
In service I think to write:
public getUsers(): Observable<User[]> {
let headers = new Headers();
headers.append('x-access-token', this.auth.getCurrentUser().token);
return this.http.get(Api.getUrl(Api.URLS.getUsers), {
headers: headers
})
.map((response: Response) => {
let res = response.json();
if (res.StatusCode === 1) {
this.auth.logout();
} else {
return res.StatusDescription.map(user=> {
return new User(user);
});
}
});
}
For me this logic work perfect. I hope to help you with this code