export class AfterContentComponent implements AfterContentChecked, AfterContentInit {
  private prevHero = '';
  comment = '';

  // Query for a CONTENT child of type `ChildComponent`
  @ContentChild(ChildComponent) contentChild: ChildComponent;

  ngAfterContentInit() {
    // contentChild is set after the content has been initialized
    this.logIt('AfterContentInit');
    this.doSomething();
  }

  ngAfterContentChecked() {
    // contentChild is updated after the content has been checked
    if (this.prevHero === this.contentChild.hero) {
      this.logIt('AfterContentChecked (no change)');
    } else {
      this.prevHero = this.contentChild.hero;
      this.logIt('AfterContentChecked');
      this.doSomething();
    }
  }
  // ...
}