Vue best practice for calling a method in a child component
I am not sure is this the best way. But I can explain what I can do... Codesandbox Demo : https://codesandbox.io/s/q4xn40935w
From parent component, send a prop
data lets say msg
. Have a button
at parent whenever click the button toggle msg
true/false
<template>
<div class="parent">
Button from Parent :
<button @click="msg = !msg">Say Hello</button><br/>
<child :msg="msg"/>
</div>
</template>
<script>
import child from "@/components/child";
export default {
name: "parent",
components: { child },
data: () => ({
msg: false
})
};
</script>
In child component watch
prop data msg
. Whenever msg
changes trigger a method.
<template>
<div class="child">I am Child Component</div>
</template>
<script>
export default {
name: "child",
props: ["msg"],
watch: {
msg() {
this.sayHello();
}
},
methods: {
sayHello() {
alert("hello");
}
}
};
</script>
I don't like the look of using props as triggers, but using ref also seems as an anti-pattern and is generally not recommended.
Another approach might be: You can use events to expose an interface of methods to call on the child component this way you get the best of both worlds while keeping your code somehow clean. Just emit them at the mounting stage and use them when pleased. I stored it in the $options part in the below code, but you can do as pleased.
Child component
<template>
<div>
<p>I was called {{ count }} times.</p>
</div>
</template>
<script>
export default {
mounted() {
// Emits on mount
this.emitInterface();
},
data() {
return {
count: 0
}
},
methods: {
addCount() {
this.count++;
},
notCallable() {
this.count--;
},
/**
* Emitting an interface with callable methods from outside
*/
emitInterface() {
this.$emit("interface", {
addCount: () => this.addCount()
});
}
}
}
</script>
Parent component
<template>
<div>
<button v-on:click="addCount">Add count to child</button>
<child-component @interface="getChildInterface"></child-component>
</div>
</template>
<script>
export default {
// Add a default
childInterface: {
addCount: () => {}
},
methods: {
// Setting the interface when emitted from child
getChildInterface(childInterface) {
this.$options.childInterface = childInterface;
},
// Add count through the interface
addCount() {
this.$options.childInterface.addCount();
}
}
}
</script>
One easy way is to do this:
<!-- parent.vue -->
<template>
<button @click="$refs.myChild.sayHello()">Click me</button>
<child-component ref="myChild" />
</template>
Simply create a ref
for the child component, and you will be able to call the methods, and access all the data it has.
You can create a ref
and access the methods, but this is not recommended. You shouldn't rely on the internal structure of a component. The reason for this is that you'll tightly couple your components and one of the main reasons to create components is to loosely couple them.
You should rely on the contract (interface in some frameworks/languages) to achieve this. The contract in Vue relies on the fact that parents communicate with children via props
and children communicate with parents via events
.
There are also at least 2 other methods to communicate when you want to communicate between components that aren't parent/child:
- the event bus
- vuex
I'll describe now how to use a prop:
Define it on your child component
props: ['testProp'], methods: { sayHello() { alert('hello'); } }
Define a trigger data on the parent component
data () { return { trigger: 0 } }
Use the prop on the parent component
<template> <div> <childComponent :testProp="trigger"/> </div> </template>
Watch
testProp
in the child component and callsayHello
watch: { testProp: function(newVal, oldVal) { this.sayHello() } }
Update
trigger
from the parent component. Make sure that you always change the value oftrigger
, otherwise thewatch
won't fire. One way of doing this is to increment trigger, or toggle it from a truthy value to a falsy one (this.trigger = !this.trigger
)