CODEWITHSUNDEEP
typescriptangular
mhusaini
mhusaini

Reputation: 1252

Angular2 - ContentChild query does not find nested components

I am trying to set up an Angular2 component that automatically focuses an input element that is inserted via content projection.

The solution I am using is based off of this answer. I have an additional requirement that the input element might be nested inside another component. However, I am finding that the ContentChild query is not able to detect elements buried deep inside ng-content tags.

@Component({
  selector: 'inner-feature',
  template: "<input auto-focus>",
  directives: [AutoFocus]
})
export class InnerFeature { }

@Component({
  selector: 'feature',
  template: `
    <div [class.hide]="!show">
      <ng-content></ng-content>
    </div>
  `
})
export class Feature {
  @ContentChild(AutoFocus)
  private _autoFocus: AutoFocus;

  private _show: boolean = false;

  @Input()
  get show() {
    return this._show;
  }
  set show(show: boolean) {
    this._show = show;
    if (show && this._autoFocus) {
      setTimeout(() => this._autoFocus.focus());
    }
  }
}

@Component({
  selector: 'my-app',
  template: `
    <div>
      <button (click)="toggleFeature()">Toggle</button>
      <feature [show]="showFeature">
        <inner-feature></inner-feature>
      </feature>
    </div>
  `,
  directives: [Feature, InnerFeature]
})
export class App {
  showFeature: boolean = false;

  toggleFeature() {
    this.showFeature = !this.showFeature;
  }
}

The _autoFocus property never gets populated. Contrast that with the case where the auto-focus directive is not nested inside another component and it works fine. Is there a way to make this work?

(I have not pasted the code for AutoFocus since it's not crucial to this example.)

See Plunker for a demo.

UPDATED code above to fix a missing directive.

Upvotes: 8

Views: 9546

Answers (2)

kodebot
kodebot

Reputation: 1778

Use ContentChildren with descendants set to true

@ContentChildren(AutoFocus, { descendants: true })

Upvotes: 9

malifa
malifa

Reputation: 8165

Actually i want to invest more time in this problem to find a better solution, but for now i came up with the following which might help you already:

First you have to expose the AutoFocus inside your InnerFeatures (and you forgot to add AutoFocus to your array of directives) using @ViewChild. This could look like this:

@Component({
  selector: 'inner-feature',
  template: "<input auto-focus>",
  directives: [AutoFocus]
})
export class InnerFeature {
  @ViewChild(AutoFocus)
  autoFocus:AutoFocus;
}

Then in your parent component Feature you could use @ContentChildren which returns a QueryList of the bound Component (in your case InnerFeature).

In your show method (or for example in or after ngAfterContentInit) you can then access this list of InnerFeatures:

export class Feature implements OnInit {
  @ContentChild(AutoFocus)
  private _autoFocus: AutoFocus;

  @ContentChildren(InnerFeature)
  private _innerFeatures: QueryList<InnerFeature>;

  private _show: boolean = false;

  @Input()
  get show() {
    return this._show;
  }
  set show(show: boolean) {
    this._show = show;
    if (show) {
      setTimeout(() => {
            if (this._autoFocus) {
                this._autoFocus.focus();
            }
            if (this._innerFeatures) {
                this._innerFeatures.map((innerFeature) => {
                    innerFeature.autoFocus.focus();
                });
            }
        });
    }
  }

  ngAfterContentInit() {
    console.log(this._autoFocus);
    console.log(this._innerFeatures);
  }
}

I modified your plunker, so you can test it in action.

Might not be as dynamic as you probably want, but well, i hope it helps anyway.

I will try to come up with a better approach , if there won't be a better answer after the England vs. Island match ;)

Update: I updated my code, cause it threw errors when accessing _results which is private. Use map() instead for the QueryList.

Upvotes: 2

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