Ionic 2 - Build Configuration-Specific Settings

May 12, 2016 · Follow on Twitter and Mastodon archive

In an Ionic 2 app that I’m building for iOS and Android, I want to use different application settings for different build configurations. Let’s see how this can be achieved in Ionic 2.

One reason that I want to be able to use different settings for different configurations, is that I want to be able to use different api endpoints for development and production apps, disable tracking for dev apps, disable logging for production apps etc.

I want to be clear that I haven’t read through the massive amount of information out there for Ionic 2, ES6, TypeScript, Angular 2 etc. If a better approach exists, please let me know.

Step 1 - Create application settings classes

I want to have a default build configuration that is shared by all build configs, then be able to override any settings and add new ones when switching configuration.

As such, I have a base class that defines most settings:

// app/config/app-settings-base

export class AppSettingsBase {
  public apiUrl: string;
  public rssFeedUrl: string;

  constructor() {
     this.apiUrl = '';
     this.rssFeedUrl = 'http://rssdomain.com/rss.xml';
  }
}

This class defines an RSS feed url, but leaves the api url blank. This means that each build configuration can define a custom RSS feed value, but must define an api url.

Note that the class isn’t injectable, which means that it can’t be injected into components in the app. For that, we will use build configuration-specific settings classes.

Let’s start off with the settings class that I will use for development:

// app/config/app-settings-debug

import {Injectable} from "angular2/core";
import {AppSettingsBase} from "../config/app-settings-base";

@Injectable()
export class AppSettings extends AppSettingsBase {
  constructor() {
    super();
    this.apiUrl = 'Debug API';
  }
}

This code contains an AppSettings class that inherits AppSettingsBase and sets a debug-specific value for the apiUrl property. This class is injectable, so we can use it in our app.

Let’s add a second settings class, that will be used for release builds:

// app/config/app-settings-release

import {Injectable} from "angular2/core";
import {AppSettingsBase} from "../config/app-settings-base";

@Injectable()
export class AppSettings extends AppSettingsBase {
  constructor() {
    super();
    this.apiUrl = 'Release API';
  }
}

This file also contains an injectable AppSettings class that also inherits AppSettingsBase (you will only use one though), then sets a release-specific value for the apiUrl property.

Step 2 -Use Gulp to apply the correct settings class

We can use Gulp to apply the correct app settings file when serving and building the app.

First, add "gulp-rename" : "1.2.2" (or later) to your package.json file. Then, require the file topmost in your gulpfile.js, like this:

rename = require('gulp-rename'),

After that, add the following build task to gulpfile.js:

gulp.task('copy-settings', function () {
  var settingsFileSuffix = isRelease ? 'release' : 'debug';
  var pathPrefix = 'app/config/app-settings-';
  return gulp
    .src(pathPrefix + settingsFileSuffix + '.ts')
    .pipe(rename('app-settings.ts'))
    .pipe(gulp.dest('app/config/'));
});

Finally, refer to this task in serve:before and build:

gulp.task('serve:before', ['watch', 'copy-settings']);

gulp.task('build', ['clean', 'copy-settings'], function(done) {

If we run ionic serve or ionic build, gulp will generate a copy of app-settings-debug.ts in app-settings.ts. If you add --release, gulp will use app-settings-release.ts instead.

You can extend this functionality to support more build configurations. Just follow the same approach as above.

Step 3 - Use the resulting settings class

We now generate a configuration-specific file every time we build or serve the app. Since it is auto-created, add app/config/app-settings.ts to .gitignore to avoid committing it.

We can now use the resulting settings class as normal. For instance, to verify that a correct settings file is applied, add the following to your app.ts file:

import {AppSettings} from './config/app-settings';

...

@App({
  ...
  providers: [PodcastService, AppSettings]
})
  export class MyApp {
    ...
    constructor(platform: Platform, settings: AppSettings) {
       console.log(settings.apiUrl);
       ...
  }
}

If things work are properly configurated, you should see different output when you build for development and for release. This means that the configuration works.

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