Instance $dispatch won't return the value

[hiendv]

Hi, I'm a little confused about the vm.$dispatch since I expected it to return values from the listener's callback for further logic which could not be placed in the callback (imo) but it turned out to be the instance it self. I'm learning Vue and probably missed something.

var vm = new Vue({
    // omitted
    events: {
        'object:creating' : function (args) {
            // omitted
            return false;
        },
        'object:created' : function (args) {
            // omitted
        }
    }
});

var child = new Vue({
    parent: vm,
    // omitted
    methods: {
        performWhatever: function (args) {
            //
        },
        createObject: function (args) {
            // Pre-create
            if ( this.$dispatch('object:creating', args) === false ) {
                // Stop the creation
            }
            // The business logic
            this.performWhatever(args);

            // Post-create
            this.$dispatch('object:created', args);
        }
    }
})

As you can see, the pre-create operation is optional.
Thank you.

[fnlctrl]

1. $dispatch has no return value.
2. Using the event system ($dispatch, $emit and so on) means your code will be asynchronous, which means what happens next is decided by the message receiver, so you don't write something like
   SomeAsyncCode === false
3. In the javascript world, we use callbacks to handle asynchronous logic (Promises are better but it's not applicable here), and $dispatch expects you to pass multiple arguments including a callback function.
4. Therefore, this is what you actually need:

this.$dispatch('object:creating', args, function() {
    // The business logic
    this.performWhatever(args);
})

and on the receiver's side,

events: {
    'object:creating' : function (args, callback) {
        // Do something with args and fire callback (or not)
        callback()
    }
}

[yyx990803]

Thanks @fnlctrl for the explanation :)

[hiendv]

@fnlctrl Thank you for explaination. It's asynchronous, I forgot, how embarrassing =D