Migration Concepts
Ionic 2 is built on top of Angular 2, which is a complete rewrite of the original framework. All the parts of Angular you know are still there, but there are new syntax and structural changes about which developers need to be aware. For an overview of the changes in Angular 2, take a look at Learn Angular 2.
In Ionic 2, things should feel quite familiar. All the concepts from Ionic V1 are still in V2, though they may look slightly different. You still have views and controllers like you did in V1, but in V2, they have been merged into one instance.
Take this V1 example.
V1
.config(function($stateProvider){
$stateProvider
.state('main', {
url: '/',
templateUrl: 'templates/main.html',
controller: 'MainCtrl'
})
})
.controller('MainCtrl', function(){
})
You can rewrite this in V2 like this:
@Page({
templateUrl:'main/main.html'
})
export class MainCmp {
constructor(){
}
}
Other changes, like navigation changes, are much different, but for good reasons, we promise. Now, you can treat components as arbitrary views and navigate to them any way you want to. This makes navigation much more flexible and allows for much more native-styled navigation stacks.
Migrating from Angular 1
While Angular 2 requires apps to be updated for the syntax change, developers can be proactive and make sure their app is upgradable by following best practices and working with John Papa’s Angular Style guide or Todd Motto’s Angular Style guide. Both of these will provide you with steps you can take to prepare your code for migration.
ControllerAs Syntax
ControllerAs Syntax is a feature in Angular 1.x where instead of binding data to $scope, you can bind to the direct instance of the controller instead. This makes migrating a Angular 1.x controller to an Angular 2 class much easier. It’s fairly easy to migrate to controllerAs from a traditional controller:
index.html
<ion-content ng-controller="MainCtrl">
<ion-item>
{{data.text}}
</ion-item>
</ion-content>
app.js
.controller('MainCtrl', function($scope){
$scope.data ={
text: 'Hello World'
}
})
To convert this to controllerAs syntax, you only have to change a few things.
index.html
<ion-content ng-controller="MainCtrl as main">
<ion-item>
{{main.data.text}}
</ion-item>
</ion-content>
app.js
.controller('MainCtrl', function(){
this.data ={
text: 'Hello World'
}
})
TypeScript
TypeScript is a superset of JavaScript that provides ES6 Classes and type annotations in your code. By adopting TypeScript now, you can write your code as ES6 Classes that will be easy to move to Ionic 2. The best part is that any valid JavaScript is also valid TypeScript, so you can convert your code piece by piece. If you take your controller from before, you can easily convert it to a TypeScript class like this.
app.js
.controller('MainCtrl', function(){
this.data ={
text: 'Hello World'
}
})
app.ts
export class MainCtrl{
constructor(){
this.data ={
text: 'Hello World'
}
}
}
Project Structure
With Angular 1, it was a practice to keep all your JavaScript together and separate from your templates. Since Ionic 2 and Angular 2 will be moving to a component base setup, you can reorganize your project to help mentally enforce that concept. So a project whose directory looks like this…
|-www/
|
|--js/
|--|-app.js
|--|-HomeCtrl.js
|--|-DetailCtrl.js
|
|--templates/
|--|-Home.html
|--|-Detail.html
|
|-index.html
could start to be reorganized to look like this:
|-www/
|
|--Home/
|--|-HomeCtrl.js
|--|-Home.html
|
|--Detail/
|--|-DetailCtrl.js
|--|-Detail.html
|
|-index.html
|-app.js
Organizing your project like this can help get you in the mindset that each of your app’s views/states are a component, with a template and a controller.