Ionic 2 blog series - Rates service

custom-storage.js

import {Storage, SqlStorage} from 'ionic/ionic';

export class CustomStorage {
  constructor() {
    this.db = new Storage(SqlStorage);
  }

  getDB() {
    return this.db._strategy._db;
  }

  query(sql, params = []) {
    return new Promise((resolve, reject) => {
      try {
        this.getDB().transaction(tx => {
          tx.executeSql(sql, params, (tx, success) => {
            resolve(success);
          }, (tx, error) => {
            reject(error);
          });
        });
      } catch (error) {
        reject(error);
      }
    });
  }
}

rates.service.js

import {CustomStorage} from '../storage/custom-storage';
import * as _ from 'lodash';

export class RatesService {
  constructor() {
    this.storage = new CustomStorage();
    this.createRatesTableIfItDoesNotExist();
  }

  all() {
    return this.storage.query('select * from rates').then(result => {
      return _.map(result.rows, row => {
        return {
          id: row.id,
          createdDate: new Date(row.createdDate),
          direction: row.direction,
          description: row.description,
          amount: row.amount,
          days: row.days,
          dailyRate: row.dailyRate
        };
      });
    }).catch(error => {
      console.log(error);
    });
  }

  create(direction) {
    return {
      createdDate: new Date(),
      direction: direction,
      description: '',
      amount: 0,
      days: 30,
      dailyRate() {
        return this.amount / this.days;
      }
    };
  }

  save(rate) {
    return this.storage.query(`insert into rates(
      createdDate,
      direction,
      description,
      amount,
      days,
      dailyRate
      ) values (?, ?, ?, ?, ?, ?)`,
      [
        rate.createdDate.getTime(),
        rate.direction,
        rate.description,
        rate.amount,
        rate.days,
        rate.dailyRate()
      ]).then(result => {
        rate.id = result.insertId;
        return rate;
      }).catch(error => {
        console.error('Error saving rate', error);
      });
  }

  createRatesTableIfItDoesNotExist() {
    const createSql = `create table if not exists rates(
      id integer primary key autoincrement,
      createdDate long,
      direction text,
      description text,
      amount real,
      days integer,
      dailyRate real
    )`;
    this.storage.query(createSql).catch(error => {
      console.error('Error creating rates table', error);
    });
  }
}