Создание директив в Angular 4

import {Directive, ElementRef, Renderer2, OnInit} from "@angular/core"; 
@Directive({ 
  selector:"[app-directive]" 
}) 
 
export class MyDirective inplements OnInit{ 
  constructor(private eleRef:ElementRef, private renderer:Renderer2){ 
  } 
  ngOnInit(){ 
   this.renderer.setStyle(this.eleRef.nativeElement,"color","blue"); 
  } 
}