simple angular directive for dropdown menu in navbar

dropdown.directive.ts

import { Directive, HostBinding, HostListener } from '@angular/core';
@Directive({
  selector: '[rbDropdown]'
})
export class DropdownDirective {

  private isOpen = false;

  @HostBinding('class.open') get opened(){
    return this.isOpen;
  }

  @HostListener('click') open(){
    this.isOpen = true;
  }


  @HostListener('mouseleave') close(){
    this.isOpen = false;
  }

}

navbar.html

<nav class="navbar navbar-default">
  <div class="container-fluid">
    <div class="navbar-header">
      <a class="navbar-brand" href="/">Site Name</a>
    </div>

    <!-- Collect the nav links, forms, and other content for toggling -->
    <div class="collapse navbar-collapse" id="bs-example-navbar-collapse-1">
      <ul class="nav navbar-nav">
        <li class="active"><a href="#">Link <span class="sr-only">(current)</span></a></li>
        <li><a href="#">Link</a></li>
      </ul>
      <ul class="nav navbar-nav navbar-right">          
        <li class="dropdown" rbDropdown>  <!-- Add dropdown directive in dropdown class -->
          <a href="#" class="dropdown-toggle">User <span class="caret"></span></a>
          <ul class="dropdown-menu">
            <li><a href="#">Login</a></li>
            <li><a href="#">Another action</a></li>
            <li role="separator" class="divider"></li>
            <li><a href="#">Logout</a></li>
          </ul>
        </li>
      </ul>
    </div><!-- /.navbar-collapse -->
  </div><!-- /.container -->
  </nav>