Getting Data with Header Authorization Ionic 2 - ruby-on-rails

Question

I'm currently working on Ionic 2 with Ruby on Rails as a backend. The issue I face is that I have trouble understanding Observables and Promises. Are they related to each other? Right now I'm trying to retrieve the data after the POST request is authenticated with the header.
//clocks.ts (Provider)
import { Injectable } from '#angular/core';
import { Http, Headers, Response, RequestOptions } from '#angular/http';
import { Storage } from '#ionic/storage';
import 'rxjs/add/operator/map';
#Injectable()
export class Clocks {
baseUrl: string = "http://localhost:3000/api/v1"
token: any;
constructor(public http: Http, public storage: Storage) {}
getAttendanceInfo() {
return new Promise((resolve,reject) => {
// Load token
this.storage.get('token').then((value) => {
this.token = value;
let headers = new Headers();
headers.append('Authorization', 'Token ' + this.token);
this.http.get(this.baseUrl + '/attendances.json', {headers: headers})
.subscribe(res => {
resolve(res);
}, (err) => {
reject(err);
})
});
});
}
At Attendance Page
//attendance.ts (Page)
loadAttendance() {
this.clocks.getAttendanceInfo().then(res => {
let response = (<Response>res).json();
this.attendance = response.data;
console.log(this.attendance)
})
}
Here are my questions.
Could I use Observables in this case to achieve the same result as the getAttendanceInfo() method? How do they work?
And also, is there any way that I can retrieve the token from the storage for every page request without rewriting the same code for headers? Eg. One method that can always be used to retrieve the token from the storage and append at the header.
Greatly appreciate if you guys can clear my confusion.

Answer 1

I've found the solution.
You can create a authentication as part of the service provider. For this case, I'm using localStorage. For the remarks, the structure of the Token is dependent for your backend as well. For my case, I'm using authentication_with_http_token from Rails method, the structure is like this
GET /attendances HTTP/1.1
Host: localhost:3000
Authorization: Token token=123123123
We have to match that.
// ../providers/auth.ts
import { Injectable } from '#angular/core';
import { Http, Headers } from '#angular/http';
import 'rxjs/add/operator/map';
#Injectable()
export class Auth {
constructor(public http: Http) {}
createAuthorizationHeader(headers: Headers) {
headers.append('Authorization', 'Token ' + window.localStorage.getItem('token'));
}
}
Wen you return a http request, it was returned in a Observable format. Unless you want to convert into Promises, you don't have to do anything about it.
// ../pages/attendances/attendances.ts
import { Component } from '#angular/core';
import { NavController } from 'ionic-angular';
import { Auth } from '../../providers/auth';
#Component({
selector: 'page-home',
templateUrl: 'home.html'
})
const baseUrl: string = 'http://localhost:3000/api/v1/';
export class HomePage {
constructor(public navCtrl: NavController, public auth: Auth) {}
ionViewDidLoad() {
this.getAttendances();
}
getAttendances() {
return this.http.get(baseUrl + 'bookings.json', { headers: headers })
.map(data => {
// convert your data from string to json
data = data.json();
})
.subscribe(response => {
// to subscribe to the stream for the response
console.log(response);
// you can save your response in object based on how you want it
})
}