for some reason emited event doesn't handles by parent component
HTML:
<template id="parent-template">
<div>
<h1>Parent: {{message}}</h1>
<child-component message="Child message"></child-component>
</div>
</template>
<template id="child-template">
<div>
<h2>Child: {{message}}</h2>
<button v-on:click="changeMessage('Changed')">Change</button>
</div>
</template>
<div id="app">
<parent-component message="Parent message"></parent-component>
</div>
JS (es5):
Child:
Vue.component("child-component", {
template: "#child-template",
props:['message'],
methods:{
changeMessage: function(newMessage){
this.message = newMessage;
this.$emit("message-changed", newMessage);
}
}
});
Parent:
Vue.component("parent-component", {
template: "#parent-template",
props:['message'],
mounted: function(){
var v = this;
this.on("message-changed", function(newValue){
alert("Emit handled!");
v.message = newValue;
});
}
});
So, everythings looks fine, but nothing happens when event fires. Why?
You cannot check for the emitted event on a mounted function, since the child Vue instances are not instantiated at that point. If you want to run the code AFTER everything has been rendered which is what I am assuming you are after then you need to run the code after a tick.
this.$nextTick(function () { // Your code goes here }
Also, for clarity, I would normally do a v-on:message-changed="parentMethod()" inside of the HTML. That way the parent is not tightly coupled to the child component at the mounted.
<child-component v-on:message-changed="parentMethod()"> </child-component>
Below is the Vue Documentation regarding the mounted information I provided:
https://v2.vuejs.org/v2/api/#mounted
Related
I am fairly new to Vue but doesn't this behavior completely contradict the design of props down, events up?
I have managed to stop it by using Object.assign({}, this.test_object ); when initializing the value in child-component but shouldn't that be the default behaviour?
Here is some background.
I am trying to have a dirty state in a much larger application (Eg a value has changed so a user must save the data back to the database before continuing on their way)
I had an event being emitted, and caught by the parent but the code I had to test the value and init the dirty state was not running as the value had already been changed in the parent component.
Vue.component( 'parent-component', {
template: '#parent-component',
data: function() {
return {
testObject: {
val: 'Test Value'
}
}
}
});
Vue.component( 'child-component', {
template: '#child-component',
props: {
test_object: Object
},
data: function() {
return {
child_object: this.test_object
}
}
});
Vue.config.productionTip = false;
new Vue({
el: '#app',
});
<script src="https://cdnjs.cloudflare.com/ajax/libs/vue/2.5.17/vue.js"></script>
<script type="text/x-template" id="parent-component">
<div>
<child-component :test_object="testObject"></child-component>
<p>This is in the parent component</p>
<p><code>testObject.val = {{testObject.val}}</code></p>
</div>
</script>
<script type="text/x-template" id="child-component">
<div>
<label for="html_input">HTML Input</label>
<input style="border:1px solid #CCC; display:block;" type="text" name="html_input" v-model="child_object.val" />
</div>
</script>
<div id="app">
<parent-component></parent-component>
</div>
Use of v-model is a very deceptive thing. If you are not careful, you might end-up mutating data that doesn't belong to your component. In your case, you are accidentally passing read-only props directly to the v-model. It doesn't know if it is a prop or a local component state.
What you are doing is the right solution but considering one-way/unidirectional data flow in mind, we can rewrite this example in more explicit and elegant fashion:
Your component definition would be:
Vue.component( 'parent-component', {
template: '#parent-component',
data: function() {
return {
testObject: {
val: 'Test Value'
}
}
},
methods: {
// Added this method to listen for input event changes
onChange(newValue) {
this.testObject.val = newValue;
// Or if you favor immutability
// this.testObject = {
// ...this.testObject,
// val: newValue
// };
}
}
});
Your templates should be:
<script type="text/x-template" id="parent-component">
<div>
<child-component :test_object="testObject"
#inputChange="onChange"></child-component>
<p>This is in the parent component</p>
<p><code>testObject.val = {{testObject.val}}</code></p>
</div>
</script>
<!-- Instead of v-model, you can use :value and #input binding. -->
<script type="text/x-template" id="child-component">
<div>
<label for="html_input">HTML Input</label>
<input type="text" name="html_input"
:value="test_object.val"
#input="$emit('inputChange', $event.target.value)" />
</div>
</script>
Key things to note:
When using v-model, ensure that you are strictly working on a local value/data of the component. By no means, it should be referenced copy of external prop.
A custom form-like component can be readily converted into the one that can work with v-model provided you accept current value as :value prop and event as #input. v-model will just work out of the box.
Any modification to the value should happen in the same component.
I'm experiencing a problem where a custom event (swap-components) emitted from a dynamic component (A.vue or B.vue) is not being listened to correctly in the parent of the dynamic component (HelloWorld.vue).
Here is the source on GitHub (created using vue cli 3).
Here is a live demo showing the problem.
In the live demo, you'll see that clicking the button in the dynamic component with background color DOES NOT change the dynamic component. But when clicking the button below the background color (which originates in the HelloWorld.vue parent), the dynamic component DOES INDEED change.
Why is this happening and how to fix it?
Below I'll copy over the contents of the 3 main files of interest into this post:
HelloWorld.vue (the parent)
A.vue (sub component used in dynamic component)
B.vue (sub component used in dynamic component)
HelloWorld.vue:
<template>
<div>
<h1>The dynamic components ⤵️</h1>
<component
:is="current"
v-bind="dynamicProps"
></component>
<button
#click="click"
>Click me to swap components from within the parent of the dynamic component</button>
</div>
</template>
<script>
import A from "./A.vue";
import B from "./B.vue";
export default {
data() {
return {
current: "A"
};
},
computed: {
dynamicProps() {
return this.current === "A" ? { data: 11 } : { color: "black" };
}
},
methods: {
click() {
this.$emit("swap-components");
},
swapComponents() {
this.current = this.current === "A" ? "B" : "A";
}
},
mounted() {
this.$nextTick(() => {
// Code that will run only after the
// entire view has been rendered
this.$on("swap-components", this.swapComponents);
});
},
components: {
A,
B
},
props: {
msg: String
}
};
</script>
A.vue:
<template>
<section id="A">
<h1>Component A</h1>
<p>Data prop sent from parent: "{{ data }}"</p>
<button #click="click">Click me to swap components from within the dynamic component</button>
</section>
</template>
<script>
export default {
props: ["data"],
methods: {
click() {
this.$emit("swap-components");
}
}
};
</script>
B.vue:
<template>
<section id="B">
<h1>Component B</h1>
<p>Color prop sent from parent: "{{ color }}"</p>
<button #click="click">Click me to swap components from within the dynamic component</button>
</section>
</template>
<script>
export default {
props: ["color"],
methods: {
click() {
this.$emit("swap-components");
}
}
};
</script>
I'm guessing this is because the event listener is listening for a swap-components event emitted by the parent component itself. Perhaps you can fix that by listening for a swap-components event from the child component then emitting an event on the parent component.
<template>
<div>
<h1>The dynamic components ⤵️</h1>
<component
:is="current"
v-bind="dynamicProps"
#swap-components="$emit('swap-components')"
></component>
<button
#click="click"
>Click me to swap components from within the parent of the dynamic component</button>
</div>
</template>
Or you can call your method directly when the event is emitted by the child component ..
<template>
<div>
<h1>The dynamic components ⤵️</h1>
<component
:is="current"
v-bind="dynamicProps"
#swap-components="swapComponents"
></component>
<button
#click="click"
>Click me to swap components from within the parent of the dynamic component</button>
</div>
</template>
this is not bound to the context anymore when you use function. It is only limited to the function scope. Use arrow function to let this bound to the parent context.
Change:
this.$nextTick(function() {
With:
this.$nextTick(() => {
I have a component with
<router-link to="page"></router-link>
<router-view></router-view>
In the Page component where the link links to, I fire an event. The component holding the link needs a subscription to that event. How do I get a reference to the Page component and subscribe to its events? As I have not explicitly declared <page></page> in the component holding the <router-link> and router-view, I can't use the normal #event syntax.
You will want to use the $root to $emit an event on and listen $on too.
Simple use anywhere in your application;
this.$root.$emit('myCustomEvent', 'hello world')
/* somewhere else in your app */
this.$root.$on('myCustomEvent', (msg) => {
/* handle the custom event */
console.log(msg)
})
Full example
<!-- src/App.vue -->
<template lang="html">
<div>
<router-link to="page">Go to Page</router-link>
<router-view></router-view>
</div>
</template>
<script>
export default {
name: 'app',
mounted () {
this.$root.$on('pageEvent', this.handlePageEvent)
},
beforeDestroy () {
// make sure you cleanup the event
this.$root.$off('pageEvent', this.handlePageEvent)
},
methods: {
handlePageEvent (ev) {
console.log('you clicked me from within')
}
}
}
</script>
<!-- src/Page.vue -->
<template>
<div>
<a #click="$root.$emit('pageEvent')">Click Me</a>
</div>
</template>
My first component (child component) like this :
<template>
...
</template>
<script>
export default {
...
methods: {
addPhoto() {
const data = { id_product: this.idProduct}
const item = this.idImage
this.$store.dispatch('addImage', data)
.then((response) => {
this.$parent.$options.methods.createImage(item, response)
});
},
}
}
</script>
If the method addPhoto called, it will call ajax and then it will get response ajax
I want to send response ajax and another parameter to method createImage. Method createImage is located in parent component (second component)
My second component (parent component) like this :
<template>
<div>
<ul class="list-inline list-photo">
<li v-for="item in items">
<div v-if="clicked[item]">
<img :src="image[item]" alt="">
<span class="fa fa-check-circle"></span>
</div>
<a v-else href="javascript:;" class="thumb thumb-upload"
title="Add Photo">
<span class="fa fa-plus fa-2x"></span>
</a>
</li>
</ul>
</div>
</template>
<script>
export default {
...
data() {
return {
items: [1,2,3,4,5],
clicked: [], // using an array because your items are numeric
test: null
}
},
methods: {
createImage(item, response) {
console.log(item)
this.$set(this.clicked, item, true)
this.test = item
},
}
}
</script>
If the code executed, it success call createImage method on parent component. The console log display value of item
But my problem is the data on parent component not success updated
How can I solve this problem?
You really should get in the habit of using events instead of directly accessing the parent component from a child.
In your case, it would be simple to emit an event in the then handler of the child's async request:
.then((response) => {
this.$emit('imageAdded', item);
});
And listen for it in the parent scope:
<child-component #itemAdded="createImage"></child-component>
That way, any component that uses that child component can react to its imageAdded event. Plus, you won't ever need to spend time debugging why the createImage method is firing when it's never being called in the Vue instance.
Your code isn't working because the way you are invoking the createImage method means that the this inside the function will not be referencing the parent component instance when it is called. So setting this.clicked or this.test will not affect the parent instance's data.
To call the parent component's function with the right context, you would need to do this:
this.$parent.createImage(item, response)
I have just started using Vue and experienced some unexpected behavior. On passing props from a parent to child component, I was able to access the prop in the child's template, but not the child's script. However, when I used the v-if directive in the parents template (master div), I was able to access the prop in both the child script and child template. I would be grateful for some explanation here, is there a better was of structuring this code? See below code. Thanks.
Parent Component:
<template>
<div v-if="message">
<p>
{{ message.body }}
</p>
<answers :message="message" ></answers>
</div>
</template>
<script>
import Answers from './Answers';
export default {
components: {
answers: Answers
},
data(){
return {
message:""
}
},
created() {
axios.get('/message/'+this.$route.params.id)
.then(response => this.message = response.data.message);
}
}
</script>
Child Component
<template>
<div class="">
<h1>{{ message.id }}</h1> // works in both cases
<ul>
<li v-for="answer in answers" :key="answer.id">
<span>{{ answer.body }}</span>
</li>
</ul>
</div>
</template>
<script>
export default{
props:['message'],
data(){
return {
answers:[]
}
},
created(){
axios.get('/answers/'+this.message.id) //only worls with v-if in parent template wrapper
.then(response => this.answers = response.data.answers);
}
}
</script>
this.message.id only works with v-if because sometimes message is not an object.
The call that you are making in your parent component that retrieves the message object is asynchronous. That means the call is not finished before your child component loads. So when your child component loads, message="". That is not an object with an id property. When message="" and you try to execute this.message.id you get an error because there is no id property of string.
You could continue to use v-if, which is probably best, or prevent the ajax call in your child component from executing when message is not an object while moving it to updated.