Angular 4 call directive method from component

问题

i'm trying to build a structural directive that will change the parent DOM structure either invoked by using its selector (static) or by calling its public method(dynamic).

• Using the directive selector in a html template works fine without any issues.

• I'm trying to figure out if we an achieve the same without using it in template and by calling the directive method.

my-directive.ts

@Directive({ selector: '[sampleDirective]' })

export class SampleDirective {
    ...
   constructor(..) {
        this.customDirective();
     }
  }
customDirective() {
    console.log('Inside customDirective()');
}

my-component.ts

import { SampleDirective } from './my.directive';
...
@Component({
 selector: 'my-component',
 template: `<button (click)="click()"> Click Me </button>`
})
constructor() { }
..
click() {
  // call directive method here
}

I need this because i'm creating a generic solution to change the DOM structure of a component at runtime with help of a directive.

** please ignore if there are any typo. sorry that i couldn't paste the complete code here

回答1:

If there's no directive in the component template Angular won't process it. With ng-container tag you will not clutter template in any way. To get the directive then use @ViewChildren/@ViewChild to get the instance of the directive:

@Component({
 selector: 'my-component',
 template: `<button (click)="click()"> Click Me </button>
            <ng-container sampleDirective></ng-container>`
})
@ViewChildren(SampleDirective) dirs;
constructor() { }
..
click() {
   this.dirs.first.customDirective();
  // call directive method here
}

回答2:

For calling directive method from component, you could use ViewChild decorator to locate directive instance on the page. Then by using the same you could access directive all props.

@ViewChild(SampleDirective) directive;
constructor() { }
..
click() {
  // call directive method here
  this.directive.customDirective()
}

来源：https://stackoverflow.com/questions/45947596/angular-4-call-directive-method-from-component