settings-service.ts

import {Injectable, Component} from 'angular2/core';
import {SqlStorage, Storage} from 'ionic-angular';

@Injectable()
export class SettingsService {
    private _storage: Storage;
    private _serverURL: String;
    constructor() {
        this._storage = new Storage(SqlStorage);
    }
    getServerURL() {
        let promise = new Promise(
            (resolve) => {
                console.log("Promise in SettingsService started");
                if (this._serverURL != null && this._serverURL != '') {
                    console.log("Promise in SettingsService resolved, already loaded");
                    resolve(this._serverURL);
                } else {
                    this._storage.get("serverURL").then(
                        data => {
                            console.log("Promise in SettingsService resolved, loaded from storage");
                            resolve(data);
                        }
                    );
                }
            }
        );
        return promise;
    }
}