Angular2 parsing from JSON to object - json

Question

I'm trying to find the best way to cast my json object to Typescript object.
I have a http get service which returns a list of user.
My current version works, I have added from JSON function to all my model classes to make the mapping works:
export class User {
constructor(
public pk: number,
public username: string,
public first_name: string,
public last_name: string,
public email: string,
public profile: UserProfile, ) {
}
static fromJSON(json: any): User {
let user = Object.create(User.prototype);
Object.assign(user, json);
user.profile = UserProfile.fromJSON(json.profile);
return user;
}
}
That works well. But there is something I don't get in the angular 2 doc. On the heroes tutorial, the JSON is automatically casted to object this way:
getHeroes (): Observable<Hero[]> {
return this.http.get(this.heroesUrl)
.map(this.extractData)
.catch(this.handleError);
}
private extractData(res: Response) {
let body = res.json();
return body.data || { };
}
I can't get this method to work on my case, I says that body.data is undefined.
Does this method really works?
EDIT:
My http service doesn't returns an array of users. It returns a page which contains an array of users in its 'results' property.
{
"count": 2,
"next": null,
"previous": null,
"results": [
{
"pk": 48,
"first_name": "Jon",
"last_name": "Does",
"profile": {
"pk": 46,
"gender": "U"
}
},
{
"pk": 47,
"first_name": "Pablo",
"last_name": "Escobar",
"profile": {
"pk": 45,
"gender": "M"
}
}
]
}
My service code:
private extractData(res: Response) {
let body = res.json().results;
return body || {}; //<--- not wrapped with data
}
search(authUser: AuthUser, terms: string): Observable<User[]> {
let headers = new Headers({
'Content-Type': 'application/json',
'X-CSRFToken': this.cookiesService.csrftoken,
'Authorization': `Token ${authUser.token}`
});
let options = new RequestOptions({ headers: headers });
return this.http.get(environment.server_url + 'user/?search=' + terms, options)
.map(this.extractData);
// .map((response: Response) => response.json());
}
My search component code:
onSearch(terms: string) {
this.searchService.search(this.user, terms).subscribe(
response => {
console.log(response); // Return array of object instead of array of user
},
error => {
console.log(JSON.stringify(error));
},
() => { }
);
}
EDIT 2:
To make this case easier, I've wrote this simple code:
test(){
let json_text=` [
{
"id": 1,
"text": "Jon Doe"
},
{
"id": 1,
"text": "Pablo Escobar"
}
]`;
console.log(<MyObject[]>JSON.parse(json_text)); // Array of objects
console.log(MyObject.fromJSON(JSON.parse(json_text))); // Array of 'MyObject'
}
export class MyObject{
id: number;
text: string;
static fromJSON(json: any): MyObject {
let object = Object.create(MyObject.prototype);
Object.assign(object, json);
return object;
}
}
console.log(<MyObject[]>JSON.parse(json_text)) returns a list of Objects
console.log(MyObject.fromJSON(JSON.parse(json_text))) returns a
list of MyObject

Answer 1

It's because in Angular tutorial, json is in the data property.
As stated in the tutorial
Make no assumptions about the server API. Not all servers return an
object with a data property.
If you are not wrapping your json with any property you can just use
private extractData(res: Response) {
let body = res.json();
return body || { }; //<--- not wrapped with data
}
Update:
Component code
onSearch(terms: string) {
this.searchService.search(this.user, terms).subscribe(
(response: SearchResponse) => { // <--- cast here
console.log(response);
},
error => {
console.log(JSON.stringify(error));
},
() => { }
);
}

Answer 2

I am quite late to this topic but found my self into the same issue . I am learning Angular and want to convert JSON received from HTTP server to my model object .
Service Class
var ele:User;
let k=this.http.get<User>(url).subscribe(data => {
ele=data;
console.log(ele.count);
console.log(ele.results[0].first_name);
console.log(ele.results[0].profile.gender);
}
);
My Model for holding the information of JSON
export interface User{
count: string;
next: string;
previous: string;
results: Result[];
}
export interface Result{
pk: string;
first_name: string;
last_name: string;
profile:Profile;
}
export interface Profile{
pk: string;
gender:string;
}
And this is it. I am using Angular 6 for parsing JSON to Object