angular - Angular2 first response to POST request undefined -

i have simple method makes post request

postdata(){   var headers = new headers();   headers.append('content-type', 'application/json');   var json = json.stringify({email: 'admin', password: 'admin'});    return this._http.post('http://localhost:8080/addressbook_rest/api/v1/contacts/login',  json ,      {headers: headers});  } 

then component call above method

onlogin() {   this._service.postdata().map(res => res.json()).subscribe(     data => { this.loggedin = data },     err => { console.log(err); }   );    console.log(this.loggedin); } 

the problem on first call, variable this.loggedin undefined after want( this.loggedin=true). don't know why gets second time.

in fact, it's because request handled asynchronously. means console.log(this.loggedin); return undefined first time because it's outside subscribe callback. it's executed before receiving request response.

you should use that:

onlogin() {   this._service.postdata().map(res => res.json()).subscribe(     data => {       this.loggedin = data;       console.log(this.loggedin); // <-------     },     err => { console.log(err); }   ); }