[Angular] Configurable Angular Components

We are going to have a modal component:

<au-modal >

</au-modal>

And we can pass default modal body by content projection:

<au-modal >
    <modal-body></modaö-body>
</au-modal>

So 'modal-body' will be shown by default. 

Now we want to modal body can be configurable. We can choose to pass in a new template thought @Input, if template was passed in then use template instead of 'modal-body':

<ng-template #newModalBody>
    <!-- template goes here-->
</ng-template>

<au-modal [body]="newModalBody">
    <au-modal-body></au-modal-body>
</au-modal>

To do that, we defined a 'ng-template' and mark it as 'newModalBody' templateRef. It contians ours new template. And we can pass the template thought @Input.

So in the au-modal, it defines:

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

@Component({
  selector: 'au-modal',
  templateUrl: './au-modal.component.html',
  styleUrls: ['./au-modal.component.scss']
})
export class AuModalComponent implements OnInit {

  @Input() body: TemplateRef<any>;
  constructor() { }

  ngOnInit() {
  }

}

In the component html, we need to check whether we pass in the template or not, if new template is present then we use it, otherwise, we fallback to default content projection:

<div class="modal-overlay">

  <div class="modal-body">

    <ng-container *ngIf="body else projectionBody">
      <ng-container *ngTemplateOutlet="body"></ng-container>
    </ng-container>

    <ng-template #projectionBody>
      <ng-content></ng-content>
    </ng-template>

  </div>

</div>

The reason here we use two ng-container is because, for one ng-container can only have one structure directive (*ngIf or *ngTeplateOutlet).