Ionic 2. Backup stories part I

When I started this blog, the idea was to practice my English with the hope to improve it, I'm self taught and I think that it is a good way to do it. Normally I write about what I'm doing, and this time is how to do a backup in my app developed with Ionic 2. The point is all of my apps don't use any server to store data, they not ask for special permissions, only the internet access for serve ads and in this case in Android, permission for write in the external storage for save the backup. But this is the second question of this story, so let's start at the beginning.

My app stores the data in a database SQLite and it to do in two tables. The amount of data is not very large and I don't need any more. My first idea was to create a method  that makes a query of all the data and store it in a file in JSON format. Create the backup is really easy and restore it not too complicated. I looked in the Ionic documentation and it provides a File API in Ionic Native for read and write files. Here you can find more info about this.  Well, it seems that I already have all of I need so let's install it.

From a terminal inside the project directory

   ionic plugin add cordova-plugin-file

And

   npm install --save @ionic-native/file

And add the plugin in the app.module.ts. First import it and then we put it on the providers section

import { File } from '@ionic-native/file';

providers: [{provide: ErrorHandler, useClass: IonicErrorHandler}, DbService, File, AdMob]

Well, it is ready to use.

But reading the documentation of the plugin I see which it have methods to check, delete and copy files. And I have thought SQLite stores the data in a file so for make a backup I only need copy this file and store it in another directory that finally is the same that should I do with the result of the query. Ok, it's already decided. I will copy the file in a directory accessible to the user.

Now the first step is find the file.  In my database service, I have wrote

openDatabase() { return this.db.openDatabase({ name: 'eDomestic.db', location: 'default', createFromLocation: 1 }) .catch(error => console.error('Error opening database', error)); }

But where is location: default. Well, in Android it is in /data/data/your-app/databases/ or using the plugin File.applicationStorageDirectory + 'databases/'. In iOS it is in /var/mobile/Applications/<UUID>/Library/LocalDatabase/  or using the plugin File.applicationStorageDirectory + 'Library/LocalDatabase/.

First we need to know what system we are using Android or iOS, for that

if (/(android)/i.test(navigator.userAgent)) { this.AndroidDir = this.file.externalRootDirectory; } else if (/(ipod|iphone|ipad)/i.test(navigator.userAgent)) { this.iOSDir = this.file.documentsDirectory; }

AndroidDir and iOSDir contains the destination for the backup. For the origin path

if (this.iOSDir.length > 1) { destPath = this.iOSDir; path = this.file.applicationStorageDirectory + 'Library/LocalDatabase/'; this.translate.get('IOSDOCUMENTSDIRECTORY') .subscribe(value => { dirMessage = value; }); } else { destPath = this.AndroidDir; path = this.file.applicationStorageDirectory + 'databases/'; this.translate.get('ANDROIDDOCUMENTSDIRECTORY') .subscribe(value => { dirMessage = value; }); }

Here, depending of what OS we are using we select a destination and origin or another. And now we can use the plugin for copy the file. But where save the file and why?

In the next entry I will continue explain the as and the why I do it like that.