In Vue 2.0 the documentation and others clearly indicate that communication from parent to child happens via props.
How does a parent tell its child an event has happened via props?
Should I just watch a prop called event? That doesn't feel right, nor do alternatives ($emit/$on is for child to parent, and a hub model is for distant elements).
I have a parent container and it needs to tell its child container that it's okay to engage certain actions on an API. I need to be able to trigger functions.
Give the child component a ref and use $refs to call a method on the child component directly.
html:
<div id="app">
<child-component ref="childComponent"></child-component>
<button @click="click">Click</button>
</div>
javascript:
var ChildComponent = {
template: '<div>{{value}}</div>',
data: function () {
return {
value: 0
};
},
methods: {
setValue: function(value) {
this.value = value;
}
}
}
new Vue({
el: '#app',
components: {
'child-component': ChildComponent
},
methods: {
click: function() {
this.$refs.childComponent.setValue(2.0);
}
}
})
For more info, see Vue documentation on refs.
What you are describing is a change of state in the parent. You pass that to the child via a prop. As you suggested, you would watch that prop. When the child takes action, it notifies the parent via an emit, and the parent might then change the state again.
var Child = {
template: '<div>{{counter}}</div>',
props: ['canI'],
data: function () {
return {
counter: 0
};
},
watch: {
canI: function () {
if (this.canI) {
++this.counter;
this.$emit('increment');
}
}
}
}
new Vue({
el: '#app',
components: {
'my-component': Child
},
data: {
childState: false
},
methods: {
permitChild: function () {
this.childState = true;
},
lockChild: function () {
this.childState = false;
}
}
})<script src="//cdnjs.cloudflare.com/ajax/libs/vue/2.2.1/vue.js"></script>
<div id="app">
<my-component :can-I="childState" v-on:increment="lockChild"></my-component>
<button @click="permitChild">Go</button>
</div>If you truly want to pass events to a child, you can do that by creating a bus (which is just a Vue instance) and passing it to the child as a prop.
You can use $emit and $on. Using @RoyJ code:
html:
<div id="app">
<my-component></my-component>
<button @click="click">Click</button>
</div>
javascript:
var Child = {
template: '<div>{{value}}</div>',
data: function () {
return {
value: 0
};
},
methods: {
setValue: function(value) {
this.value = value;
}
},
created: function() {
this.$parent.$on('update', this.setValue);
}
}
new Vue({
el: '#app',
components: {
'my-component': Child
},
methods: {
click: function() {
this.$emit('update', 7);
}
}
})
Running example: https://jsfiddle.net/rjurado/m2spy60r/1/