[Angular 2] Create Shareable Angular 2 Components

Components that you use across multiple applications need to follow a module pattern that keeps them separate from your application logic. This will allow you to make these Angular 2 components reusable and shareable and is the same pattern followed by many libraries that you may import into your projects.

The structure likes this:

In widget-one.component.html. we use *ngIf to control the display, to do this, we have to import CommonModule from angular/common, which inlcudes NgIf, NgFor.... 

import { NgModule} from '@angular/core';
import { CommonModule } from '@angular/common';
import {WidgetOneComponent} from './widget-one.component';
import {WidgetTwoComponent} from './widget-two.component';

@NgModule({
    imports: [CommonModule],
    declarations: [WidgetOneComponent, WidgetTwoComponent],
    exports: [WidgetOneComponent, WidgetTwoComponent, CommonModule]
})
export class WidgetsModule {

}

The CommonModule is available for root Module. When you create a sub module, it won't import CommonModule by default, so you need to imports it and exprots it to other sub module for free.  

widget-one.component.ts:

import { Component, OnInit } from '@angular/core';

@Component({
    moduleId: module.id,
    selector: 'widget-one',
    templateUrl: '<div *ngIf=selected'This is widget one </div>
})
export class WidgetOneComponent implements OnInit {
    selected = false;
    constructor() { }

    ngOnInit() { }
    
}