问题描述

我正在尝试编写一个 Angular2 属性指令来修改某些元素的行为.更具体地说，我想将属性应用于具有点击处理程序的某些元素，并防止绑定函数在某些条件下执行.

I am trying to write a Angular2 attribute directive to modify the behaviour of certain elements. More specifically I want to apply an attribute to certain elements that have click handlers and prevent the bound function to be executed under certain conditions.

所以现在我有一个元素，例如:

So now I have an element e.g.:

<button (click)="onClick(param1, param2)"></button>

onClick 是在承载按钮元素的组件上声明的函数.

onClick is a function declared on the component that hosts the button element doing some work.

我想做的是这样写:

<button (click)="onClick(param1, param2)" online-only></button>

并有一个类似的指令:

@Directive({
  selector: '[online-only]',
})
export class OnlineOnlyDirective {
  @HostListener('click', ['$event']) 
  onClick(e) {
    if(someCondition){
      e.preventDefault();
      e.stopPropagation();
    }
  }
}

但是单击处理程序首先执行，因此我的指令没有机会停止执行.

But click handler is executed first, thus not giving my directive the opportunity to stop its execution.

我想到的第二种方法是用我自己的处理程序替换(单击)，例如([onlineClick]="onClick")并在指令认为合适时执行传递的函数，但是这样我不能将参数传递给 onClick 函数和看起来有点奇怪.

A second approach I thought about was replacing (click) with my own handler e.g.( [onlineClick]="onClick" ) and execute the passed function when the directive thinks fit, but this way I cannot pass params to onClick function and is a bit weirder to look at.

你对做这样的事情有什么想法吗?

Do you have any thoughts on doing something like that?

推荐答案

我不知道有什么方法可以强制 Angular 先执行某个事件处理程序.一种解决方法可能是使用自定义事件，例如:

I don't know of a way to force Angular to execute a certain event handler first. A workaround might be to use a custom event like:

<button (myClick)="onClick(param1, param2)" online-only></button>

@Directive({
  selector: '[myClick]',
})
export class OnlineOnlyDirective {
  @Output() myClick: EventEmitter = new EventEmitter();
  @HostListener('click', ['$event']) 
  onClick(e) {
    if(someCondition){
      e.preventDefault();
      e.stopPropagation();
    } else {
      this.myClick.next(e);
    }
  }
}

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