Use vm.$on to listen to event emitted from child i

问题:

I've been through the vue.js events section on events but it seems to only give examples of how to listen to events using the vm.$on handler within html. Between that and the new changes for 2.0 I'm unsure how to simply transmit a event from child -> parent.

I need to transmit an event because after parent receiving i want to broadcast it to another child.

I'm using single page components, this is my setup:

// parent
export default {
  mounted: function () {
    this.$on('myEvent', function (msg) {
    console.log('caught in parent', msg)
  });
 },
 components: {
  'child': child,
 },
}

// child
this.$emit('myEvent', true)

How can I receive this event on the parent vm please? Note, I don't want to use $on in the html. I want the event receiving logic in the vm where it should be.

Thanks,

回答1:

Vues documentation on $emit is not very comprehensive, however, there are a few ways to do this. Firstly you have to $emit on the vue model you want to send the message to if you want to use this.$on(), so if you are sending from a component you can emit to the direct parent using:

this.$parent.$emit('myEvent',true);

However, this can become problematic if you have a long chain of parents because you have to $emit up the child chain, so in that case you can use a Vue instance as a bus:

// In the root as a global variable so all components have access
var bus = new Vue({});

Or if you are using single file components.

window.bus = new Vue({});

Then in the receiver:

bus.$on('myEvent',() => {
   // Do stuff
});

And in the emitter:

bus.$emit('myEvent',true);

Finally, if you find you app getting too complex for a simple bus then you can use vuex:

https://vuex.vuejs.org/en/index.html