How do I conditionally wrap <ng-content> multiple times?

Question

I tried writing a wrapper component which can be passed some text and some parameters, which would then format my text using bootstrap, based on these parameters.

I've tried this:

header-line.component.ts

@Component({
  selector:'header-line',
  templateUrl: 'header-line.component.html'
})
export class HeaderLineComponent {
  @Input level: number;
  // other inputs used for formatting skipped here
}

header-line.component.html

<div class="row">
  <div class="col-sm-12"> <!-- would really be [className]="..." based on skipped inputs -->
    <header-wrapper [level]="level">
      <!-- display of icon, based on skipped inputs -->
      <ng-content></ng-content>
    </header-wrapper>
  </div>
</div>

header-wrapper.component.ts

@Component({
  selector: 'header-wrapper',
  templateUrl: './header-wrapper.component.html'
})
export class HeaderWrapperComponent {
  @Input() level: number;
}

header-wrapper.component.html

<h1 *ngIf="level === 1"><ng-content></ng-content></h1>
<h2 *ngIf="level === 2"><ng-content></ng-content></h2>
<h3 *ngIf="level === 3"><ng-content></ng-content></h3>
<h4 *ngIf="level === 4"><ng-content></ng-content></h4>
<h5 *ngIf="level === 5"><ng-content></ng-content></h5>
<span *ngIf="!level || level < 1 || level > 5"><ng-content></ng-content></span>

Intended usage

Usage would be something along the lines of:

<header-line [level]="1" [...]="...">Just a test h1</header-line>
<header-line [level]="2" [...]="...">Just a test h2</header-line>
<header-line [level]="3" [...]="...">Just a test h3</header-line>
<header-line [...]="...">Just a test span</header-line>

Expected output

I would then have expected the output to create something equivalent to:

<div class="row">
  <div class="cols-sm-12">
    <h1>Just a test h1</h1>
  </div>
</div>
<div class="row">
  <div class="cols-sm-12">
    <h2>Just a test h2</h2>
  </div>
</div>
<div class="row">
  <div class="cols-sm-12">
    <h3>Just a test h3</h3>
  </div>
</div>
<div class="row">
  <div class="cols-sm-12">
    <span>Just a test span</span>
  </div>
</div>

Effective output

However, what I do get is the following:

<div class="row">
  <div class="cols-sm-12">
  </div>
</div>
<div class="row">
  <div class="cols-sm-12">
  </div>
</div>
<div class="row">
  <div class="cols-sm-12">
  </div>
</div>
<div class="row">
  <div class="cols-sm-12">
    <span>Just a test span</span>
  </div>
</div>

Problem analysis

It took me only a little while to find out that the cause of my problem is the repeated use of in header-wrapper.component.ts because it is apparently static and cannot be used dynamically.

The following two links explain why my expectations were disappointed:

https://github.com/angular/angular/issues/9173

https://github.com/angular/angular/issues/8563

Finding a solution

The following link on Stackoverflow shows how this can be done if only two cases need to be supported:

How to conditionally wrap a div around ng-content

Using that approach I managed the following:

Updated: header-wrapper.component.html

<h1 *ngIf="level && level === 1; else notOne">
  <ng-container *ngTemplateOutlet="content"></ng-container>
</h1>

<ng-template #notOne>
  <h2 *ngIf="level && level === 2; else notTwo">
    <ng-container *ngTemplateOutlet="content"></ng-container>
  </h2>
</ng-template>

<ng-template #notTwo>
  <h3 *ngIf="level && level === 3; else notThree">
    <ng-container *ngTemplateOutlet="content"></ng-container>
  </h3>
</ng-template>

<ng-template #notThree>
  <h4 *ngIf="level && level === 4; else notFour">
    <ng-container *ngTemplateOutlet="content"></ng-container>
  </h4>
</ng-template>

<ng-template #notFour>
  <h5 *ngIf="level && level === 5; else content">
    <ng-container *ngTemplateOutlet="content"></ng-container>
  </h5>
</ng-template>

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

This produces the desired output.

My question

Is this really the only way to do this? Or is there an easier way that I am missing?

Answer 1

Based on the video linked by Jota.Toledo I have come up with a more compact version.

Updated header-wrapper.component.html

<h1 *ngIf="level && level === 1"><ng-container [ngTemplateOutlet]="content"></ng-container></h1>
<h2 *ngIf="level && level === 2"><ng-container [ngTemplateOutlet]="content"></ng-container></h2>
<h3 *ngIf="level && level === 3"><ng-container [ngTemplateOutlet]="content"></ng-container></h3>
<h4 *ngIf="level && level === 4"><ng-container [ngTemplateOutlet]="content"></ng-container></h4>
<h5 *ngIf="level && level === 5"><ng-container [ngTemplateOutlet]="content"></ng-container></h5>
<span *ngIf="!level || level < 1 || level > 5"><ng-container [ngTemplateOutlet]="content"></ng-container></span>

This works just the same as my updated solution from the question, but I find this version more compact and more easily readable.