I am just starting out with angular and i am facing some issues with async operations. I am trying to set a class private value to a localstorage key value that will be used in a http request, but the http reuqest fires off before the key can be retrieved from the storage. I am using ionic native storage. What is the proper way to implement this operation? Any help would be much appreciated. Here is my code:
export class EventService {
constructor(private _http: Http, private _storage: Storage) {
}
private url = 'http://website.com';
private token : string;
getEventsAction() {
this._storage.ready().then(() => {
this._storage.get('auth_token').then((val) => {
this.token = val;
});
});
let params = {
"query": {
"search_term": "", "page": 1
}
};
let headers = new Headers();
headers.append('Content-Type', 'application/x-www-form-urlencoded');
headers.append('Access-Control-Allow-Origin', '*');
headers.append('Auth-Token', this.token);
let options = new RequestOptions({headers: headers});
return this._http.post(this.url + '/api/events/list', params, options)
.map((response: Response) => {
let events = response.json();
if (events) {
return events;
}
});
}
You have to send the http request after the storage callback has been called. This is your code updated with private methods in order to make to code cleaner :
export class EventService {
constructor(private _http: Http, private _storage: Storage) { }
private url = 'http://website.com';
private token : string;
getEventsAction() {
this.retrieveToken().catch(() => {
// You can log something here, the 'then' callback will be always executed anyway
}).then(() => {
this.sendHttpRequest();
});
}
private retrieveToken(): Promise<any> {
return this._storage.ready().then(() => {
return this._storage.get('auth_token').then((val) => {
this.token = val;
}).catch(() => {
// Set default token if storage.get() raised an exception
this.token = 'defaultToken';
});
});
}
private sendHttpRequest() {
let params = {
"query": {
"search_term": "", "page": 1
}
};
let headers = new Headers();
headers.append('Content-Type', 'application/x-www-form-urlencoded');
headers.append('Access-Control-Allow-Origin', '*');
headers.append('Auth-Token', this.token);
let options = new RequestOptions({headers: headers});
return this._http.post(this.url + '/api/events/list', params, options)
.map((response: Response) => {
let events = response.json();
if (events) {
return events;
}
});
}
}
The technical post webpages of this site follow the CC BY-SA 4.0 protocol. If you need to reprint, please indicate the site URL or the original address.Any question please contact:yoyou2525@163.com.