Components are the backbone of Angular and Ionic applications; you will see that almost everything is a component. You can compare controllers in Angular 1 to components in Angular 4. In controllers we used to define most of our code's logical part. We used to register the controllers with our main module. Now, in a similar way, we define our code in components in Angular 4 and if required we can export that Component class:
// Angular & Ionic 1angular.module('wedding.controllers', []) .controller('LoginCtrl', function($scope, CategoryService) { // controller function and DI of CategoryService } );// Angular 4 & Ionic 32import {Component} from '@angular/core';import {NavController} from 'ionic-angular';@Component({ ...
