Vue.js - Emit event from directive

euvl picture euvl · Nov 17, 2016 · Viewed 13.6k times · Source

Is it possible to emit a custom event from the directive in the component to which this directive is attached.

I was expecting it to work as described in example, but it does not.

Example:

//Basic Directive
<script>
  Vue.directive('foo', {
    bind(el, binding, vnode) {
      setTimeout(() => {
        //vnode.context.$emit('bar'); <- this will trigger in parent
        vnode.$emit('bar');
      }, 3000);
    }
  });
</script>


//Basic Component
<template>
  <button v-foo @bar="change">{{label}}</button>
</template>
<script>
  export default{
    data() {
      return {
        label: 'i dont work'
      }
    },
    methods: {
      change() {
        this.label = 'I DO WORK!';
      }
    }
  }
</script>

Any ideas on the matter? Am I missing something?

JSFiddle: https://jsfiddle.net/0aum3osq/4/

Update 1:

Okay, i've found that if I call vnode.data.on.bar.fn(); (or fns() in latest Vue versions) in directive it will trigger bar event handler.

Update 2:

Temporary solution:

  /*temp. solution*/
  var emit = (vnode, name, data) => {
    var handlers = vnode.data.on;

    if (handlers && handlers.hasOwnProperty(name)) {
      var handler = handlers[name];
      var fn = handler.fns || handler.fn;

      if (typeof fn === 'function') {
        fn(data);
      }
    }
  } 

//Basic Directive
<script>
  Vue.directive('foo', {
    bind(el, binding, vnode) {
      setTimeout(() => {
        emit(vnode, 'bar');
      }, 3000);
    }
  });
</script>

Answer

euvl picture euvl · Nov 21, 2016

So the solution I am using in Vue 2+ (considering there were no answers so far):

In directive add method:

var emit = (vnode, name, data) => {
  var handlers = (vnode.data && vnode.data.on) ||
    (vnode.componentOptions && vnode.componentOptions.listeners);

  if (handlers && handlers[name]) {
    handlers[name].fns(data);
  }
}

And call it this way:

bind(el, binding, vnode) {
  emit(vnode, 'bar' , {some: 'event', data: 'here'});
}

The benefits of an approach:

1 Keep the same code-style in your project, meaning that every handler can be declared as
v-on:handler_name and be handled in meaningful (for developer) way. Other solutions, like sending callback as parameter, are sometimes confusing and not obvious without digging into documentation/code.

2 Using built-in events system also allows to gracefully handle event objects. For example, this code will work perfectly fine:

<button v-foo @bar="bar(1, $event, 2)">{{label}}</button>
...
methods: {
  bar(one, event, two) { console.log(one, event, two); }
} 

EDIT:

In v2.1+ you can use this inside directive binding:

vnode.context.$emit(eventname)