Angular2指令属性绑定

Question

I have a directive that either shows or hides a sidebar on click. I want to create an option to show the sidebar or hide the sidebar on i.

My component.html:

<button class="sidebar-minimizer" type="button" appSidebarMinimizer [minimizeSide] = "open" appBrandMinimizer></button>

I created a property [minimizeSide] = "'open'"

My component.ts

export class AppSidebarMinimizerComponent {
  open = "open";

}

My directive:

@Directive({
  selector: '[appSidebarMinimizer]'
})
export class SidebarMinimizeDirective {
  @Input() minimizeSide:string;
  constructor() {
    if (this.minimizeSide == "open"){
      document.querySelector('body').classList.toggle('brand-minimized');
    }
  }

  @HostListener('click', ['$event'])
  toggleOpen($event: any) {
    $event.preventDefault();
    document.querySelector('body').classList.toggle('sidebar-minimized');
  }
}

The click function works fine but it doesn't work while init. What am I missing?

Answer 1

Here the reason to your problem are listed below:

• @Input field will be updated when first change detection got executed
• Directive, as also Component, will be constructed first and then runs life-hook ( OnChanges => OnInit and so on)of itself.

So you won't get value bound to @Input unless OnChange life hook of your directive got executed. You can move the initialization code block to directive's OnInit life hook.

constructor() { }

ngOnInit() {
  if (this.minimizeSide == "open"){
    document.querySelector('body').classList.toggle('brand-minimized');
  }
}