How to pass data from child to parent component in vue?

How to pass data from child to parent component in vue? - javascript

I am using Vue.Js where i am calling my child component multiple times from parent. Which means there are separate instance created for all the different call. Data "json" will contain seperate value for all the different instance.
Now i want to fetch data present in variable json in all the instance of child component from parent component.
[Code]
Parent component
<div v-for="(value, index) in inputs" :key="index++">
<ChildComponent :componentcount="index" ></ChildComponent>
</div>
Child Component
<template>
<div id="hello">
<div>
<v-text-field :id="'ComponentHeader_' + $attrs.componentcount" v-model="header"
class="headertag" label="Child Tag" #change="createJson" outlined>
</v-text-field>
</div>
</div>
</template>
<script>
export default {
data(){
return{
json:"",
}
}
}

You can use $emit method for this purpose.
v-on directive captures the child components events that is emitted by $emit
Child component triggers clicked event:
export default {
methods: {
onClickButton (event) {
this.$emit('clicked', 'someValue')
}
}
}
Parent component receive clicked event:
<div>
<child #clicked="onClickChild"></child>
</div>
export default {
methods: {
onClickChild (value) {
console.log(value) // someValue
}
}
}

Related

Vue parent-child emit function is breaking v-model binding

Working on fixing a bug in someone else's code, so I'm trying to limit what I have to change here.
Seems like when I use $emit functionality to run functions between child and parent components, v-model binding is being lost in my components.
There is a parent component:
ParentComponent.vue
<template>
<child-component v-bind:items="this.items"
v-on:event_child="this.eventUpdater">
</child-component>
<template>
<script>
import ChildComponent from './ChildComponent.vue';
export default {
components: {
'child-component': ChildComponent
},
methods: {
getItemDetails() {
//...ajax request that loads item details for page.
},
eventUpdater: function(id) {
this.getItemDetails();
}
}
}
</script>
Then, there is a child component:
ChildComponent.vue
<template>
<div v-for="item in items">
<input v-model="item.itemId">
</div>
<button v-on:click="updateItems">update</button>
</template>
<script>
export default {
props: ['items'],
methods: {
updateItems() {
//...ajax call that updates items.
this.emitWhat();
},
emitWhat: function () {
this.$emit('event_child');
}
}
}
</script>
After updating my initial item (which updates fine), I go to update another item, and it seems like the v-model for that item does not work. Is the $emit functionality breaking the v-model binding after initially loading? How do I fix this?

You are using this:
<child-component v-bind:items="this.items"
v-on:event_child="this.eventUpdater">
but should use this:
<child-component v-bind:items="items"
v-on:event_child="eventUpdater">
Removed this..
Also I didn't find items as data property in parent component.
Upd.
Also if you define id parameter in eventUpdater: function(id) method you should emit it like this:
<template>
<div v-for="item in items">
<input v-model="item.itemId">
</div>
<button v-on:click="updateItems(item.itemId)">update</button>
</template>
updateItems(id) {
//...ajax call that updates items.
this.emitWhat(id);
},
emitWhat: function (id) {
this.$emit('event_child', id);
}
Upd.2
Also you have v-model on item.itemId which could be a problem:
<input v-model="item.itemId">
You could consider to bind v-model to newItems like this:
<input v-model="newItems[itemId]">
data(){
return {
newItems: [],
//...
};
}

Update props value in child component in vue

parent.vue
<template>
...
<div>{{ meet}} </div>
...
</template>
...
props: ["meet"]
child.vue
<template>
...
<meet :meet="showMeet(e.id)" />
</template>
...
props: ['meet'],
...
methods: {
showMeet(id) {
this.meet == 'abc';
}
}
How do i update the value of the props to be used in child component

You may need to re-render the child component again. As per my understanding so far, the same prop is present in both the child's and if you update it's value from one, then you want to update it in second too. Refer this
https://michaelnthiessen.com/force-re-render/

Dynamically loading child components in parent component

I am a beginner in Vue.js so please bear with me. I created two child components and one parent component. I am able to load both the components in the parent components. Now, one of my child component should load in the parent component by default. It will have a link, and when clicked, it should load the other child component within the same parent component, by passing and ID value from itself to the loading component. Below is my code.
Parent component (App.vue):
<template>
<div id="app">
<body>
<main>
<div class="main-body">
<component v-bind:is="currentComp">
</component>
</div>
</main>
</body>
</div>
</template>
<script>
import HomeContent from './components/HomeContent.vue';
import DetailContent from './components/DetailContent.vue';
import { changeRoute } from './main.js';
export default {
name: 'app',
data() {
return {
currentComp: 'HomeContent'
};
},
components: {
HomeContent, //this is the default child component
DetailContent, //this is the other child component which should get loaded dynamically
},
created() {
changeRoute.$on('switchComp', comp => {
this.currentComp = comp;
})
}
}
</script>
Default child component (HomeContent.vue):
<template>
<div>
This is Default child component
Click to load the other child dynamically
</div>
</template>
<script>
import { changeRoute } from '../main.js';
export default {
name: 'HomeContent',
props: {
msg: String
},
methods: {
switchComponent(comp) {
changeRoute.$emit('switchComp', comp);
}
}
}
</script>
The other child component (DetailContent):
<template>
<div>
This is the other loaded child component.
</div>
</template>
<script>
export default {
name: 'DetailContent',
props: {
msg: String
},
mounted(){
alert('mount ok');
}
}
</script>
With the above approach DetailContent get loaded on click of a link from the HomeContent. Now, how can pass some data (e.g. ID = 1) from HomeContent to DetailContent. Any help with this please?

Executing child (component) function from the parent component

To avoid this becoming messy and the use of "native" jQuery/javascript I would like to call a function in the child component from the parent, the function I want to exeecute is change_map_data() from the child G_Map.vue in an elegant way, vueish way:
Parent.vue
<template>
<div class="col-md-12">
...
<i v-on:click="change_map_data">change markers</i>
...
<g-map v-bind:map_data="init_data.map"></g-map>
...
</div>
export default {
data() {
return {
init_data: {
map: {
map_ele: 'map'
}
}
}
}
}
</script>
</template>
G_Map.vue:
<template>
<div :id="map_data.map_ele" class="gmap"></div>
</template>
<script>
import init_map from '../../../assets/js/map.js';
export default {
props: ['map_data'],
methods: {
change_map_data: function() { // want to execute this from parent
alert();
}
}
}
</script>

If you want to call a method defined on a child component from the parent component, you'll have to get a reference to the child component and call its method directly:
<i v-on:click="$refs.map.change_map_data()">change markers</i>
<g-map v-bind:map_data="init_data.map" ref="map"></g-map>
If you're generating a dynamic number of maps, then you'll need to do something like this:
<div v-for="map, i of maps">
<i v-on:click="$refs.map[i].change_map_data()">change markers</i>
<g-map v-bind:map_data="map" ref="map"></g-map>
</div>

vuejs update parent data from child component

I'm starting to play with vuejs (2.0).
I built a simple page with one component in it.
The page has one Vue instance with data.
On that page I registered and added the component to html.
The component has one input[type=text]. I want that value to reflect on the parent (main Vue instance).
How do I correctly update the component's parent data?
Passing a bound prop from the parent is not good and throws some warnings to the console. They have something in their doc but it is not working.

Two-way binding has been deprecated in Vue 2.0 in favor of using a more event-driven architecture. In general, a child should not mutate its props. Rather, it should $emit events and let the parent respond to those events.
In your specific case, you could use a custom component with v-model. This is a special syntax which allows for something close to two-way binding, but is actually a shorthand for the event-driven architecture described above. You can read about it here -> https://v2.vuejs.org/v2/guide/components.html#Form-Input-Components-using-Custom-Events.
Here's a simple example:
Vue.component('child', {
template: '#child',
//The child has a prop named 'value'. v-model will automatically bind to this prop
props: ['value'],
methods: {
updateValue: function (value) {
this.$emit('input', value);
}
}
});
new Vue({
el: '#app',
data: {
parentValue: 'hello'
}
});
<script src="https://cdnjs.cloudflare.com/ajax/libs/vue/2.5.13/vue.js"></script>
<div id="app">
<p>Parent value: {{parentValue}}</p>
<child v-model="parentValue"></child>
</div>
<template id="child">
<input type="text" v-bind:value="value" v-on:input="updateValue($event.target.value)">
</template>
The docs state that
<custom-input v-bind:value="something" v-on:input="something = arguments[0]"></custom-input>
is equivalent to
<custom-input v-model="something"></custom-input>
That is why the prop on the child needs to be named value, and why the child needs to $emit an event named input.

In child component:
this.$emit('eventname', this.variable)
In parent component:
<component #eventname="updateparent"></component>
methods: {
updateparent(variable) {
this.parentvariable = variable
}
}

From the documentation:
In Vue.js, the parent-child component relationship can be summarized as props down, events up. The parent passes data down to the child via props, and the child sends messages to the parent via events. Let’s see how they work next.
How to pass props
Following is the code to pass props to a child element:
<div>
<input v-model="parentMsg">
<br>
<child v-bind:my-message="parentMsg"></child>
</div>
How to emit event
HTML:
<div id="counter-event-example">
<p>{{ total }}</p>
<button-counter v-on:increment="incrementTotal"></button-counter>
<button-counter v-on:increment="incrementTotal"></button-counter>
</div>
JS:
Vue.component('button-counter', {
template: '<button v-on:click="increment">{{ counter }}</button>',
data: function () {
return {
counter: 0
}
},
methods: {
increment: function () {
this.counter += 1
this.$emit('increment')
}
},
})
new Vue({
el: '#counter-event-example',
data: {
total: 0
},
methods: {
incrementTotal: function () {
this.total += 1
}
}
})

Child Component
Use this.$emit('event_name') to send an event to the parent component.
Parent Component
In order to listen to that event in the parent component, we do v-on:event_name and a method (ex. handleChange) that we want to execute on that event occurs
Done :)

I agree with the event emitting and v-model answers for those above. However, I thought I would post what I found about components with multiple form elements that want to emit back to their parent since this seems one of the first articles returned by google.
I know the question specifies a single input, but this seemed the closest match and might save people some time with similar vue components. Also, no one has mentioned the .sync modifier yet.
As far as I know, the v-model solution is only suited to one input returning to their parent. I took a bit of time looking for it but Vue (2.3.0) documentation does show how to sync multiple props sent into the component back to the parent (via emit of course).
It is appropriately called the .sync modifier.
Here is what the documentation says:
In some cases, we may need “two-way binding” for a prop.
Unfortunately, true two-way binding can create maintenance issues,
because child components can mutate the parent without the source of
that mutation being obvious in both the parent and the child.
That’s why instead, we recommend emitting events in the pattern of
update:myPropName. For example, in a hypothetical component with a
title prop, we could communicate the intent of assigning a new value
with:
this.$emit('update:title', newTitle)
Then the parent can listen to
that event and update a local data property, if it wants to. For
example:
<text-document
v-bind:title="doc.title"
v-on:update:title="doc.title = $event"
></text-document>
For convenience, we offer a shorthand for this pattern with the .sync modifier:
<text-document v-bind:title.sync="doc.title"></text-document>
You can also sync multiple at a time by sending through an object. Check out the documentation here

The way more simple is use this.$emit
Father.vue
<template>
<div>
<h1>{{ message }}</h1>
<child v-on:listenerChild="listenerChild"/>
</div>
</template>
<script>
import Child from "./Child";
export default {
name: "Father",
data() {
return {
message: "Where are you, my Child?"
};
},
components: {
Child
},
methods: {
listenerChild(reply) {
this.message = reply;
}
}
};
</script>
Child.vue
<template>
<div>
<button #click="replyDaddy">Reply Daddy</button>
</div>
</template>
<script>
export default {
name: "Child",
methods: {
replyDaddy() {
this.$emit("listenerChild", "I'm here my Daddy!");
}
}
};
</script>
My full example: https://codesandbox.io/s/update-parent-property-ufj4b

It is also possible to pass props as Object or Array. In this case data will be two-way binded:
(This is noted at the end of topic: https://v2.vuejs.org/v2/guide/components.html#One-Way-Data-Flow )
Vue.component('child', {
template: '#child',
props: {post: Object},
methods: {
updateValue: function () {
this.$emit('changed');
}
}
});
new Vue({
el: '#app',
data: {
post: {msg: 'hello'},
changed: false
},
methods: {
saveChanges() {
this.changed = true;
}
}
});
<script src="https://cdnjs.cloudflare.com/ajax/libs/vue/2.5.13/vue.js"></script>
<div id="app">
<p>Parent value: {{post.msg}}</p>
<p v-if="changed == true">Parent msg: Data been changed - received signal from child!</p>
<child :post="post" v-on:changed="saveChanges"></child>
</div>
<template id="child">
<input type="text" v-model="post.msg" v-on:input="updateValue()">
</template>

In Parent Conponent -->
data : function(){
return {
siteEntered : false,
};
},
In Child Component -->
this.$parent.$data.siteEntered = true;

2021 ANSWER - Vue 2.3+
SHORT ANSWER: Just add .sync modifier in the parent and pass the data as props to the children:
// PARENT:
data () {
return {
formData: {
members: [] //<- we wanna pass this one down to children and add/remove from the child component
}
}
// PARENT TEMPLATE:
<!-- ADD MEMBERS -->
<add-members :members.sync="formData.members" />
Nested child component: AddMembers.vue
export default {
name: 'AddMembers',
props: ['members'],
methods: {
addMember () {
this.members.push(new Member()) // <-- you can play and reactivity will work (in the parent)
},
removeMember (index) {
console.log('remove', index, this.members.length < 1)
this.members.splice(index, 1)
}
}
}
Long story: changes from the child component in reallity are being $emitted and updating formData.members[] of the parent.
source: Mauro Perez at medium

In the child
<input
type="number"
class="form-control"
id="phoneNumber"
placeholder
v-model="contact_number"
v-on:input="(event) => this.$emit('phoneNumber', event.target.value)"
/>
data(){
return {
contact_number : this.contact_number_props
}
},
props : ['contact_number_props']
In parent
<contact-component v-on:phoneNumber="eventPhoneNumber" :contact_number_props="contact_number"></contact-component>
methods : {
eventPhoneNumber (value) {
this.contact_number = value
}

The correct way is to $emit() an event in the child component that the main Vue instance listens for.
// Child.js
Vue.component('child', {
methods: {
notifyParent: function() {
this.$emit('my-event', 42);
}
}
});
// Parent.js
Vue.component('parent', {
template: '<child v-on:my-event="onEvent($event)"></child>',
methods: {
onEvent: function(ev) {
v; // 42
}
}
});

When we want to pass the data to the parent component as well as another nested child component of the current child component, using a data property would be useful as shown in the following example.
Example:
Calling your child component from the parent component like this.
Parent component:
<template>
<TodoItem :todoParent="todo" />
</template>
<script>
export default {
data() {
return {
todo: {
id:1,
task:'todo 1',
completed:false
}
};
}
}
</script>
Child component:
<template>
<div class="todo-item" v-bind:class="{'is-completed':todo.completed}">
<p>
<input type="checkbox" #change="markCompleted" />
{{todo.task}}
<button class="del">x</button>
</p>
</div>
</template>
<script>
export default {
name: "TodoItem",
props: ["todoParent"],
data() {
return {
todo: this.todoParent,
};
},
methods: {
markCompleted() {
this.todo.completed = true
},
},
};
</script>
Even you can pass this property to the nested child component and it won't give this error/warning.
Other use cases when you only need this property sync between parent and child component. It can be achieved using the sync modifier from Vue. v-model can also be useful. Many other examples are available in this question thread.
Example2: using component events.
We can emit the event from the child component as below.
Parent component:
<template>
<TodoItem :todo="todo" #markCompletedParent="markCompleted" />
</template>
<script>
export default {
data() {
return {
todo: {
id:1,
task:'todo 1',
completed:false
}
};
},
methods: {
markCompleted() {
this.todo.completed = true
},
}
}
</script>
Child component:
<template>
<div class="todo-item" v-bind:class="{'is-completed':todo.completed}">
<p>
<input type="checkbox" #change="markCompleted" />
{{todo.task}}
<button class="del">x</button>
</p>
</div>
</template>
<script>
export default {
name: "TodoItem",
props: ["todo"],
methods: {
markCompleted() {
this.$emit('markCompletedParent', true)
},
}
};
</script>

Another way is to pass a reference of your setter from the parent as a prop to the child component, similar to how they do it in React.
Say, you have a method updateValue on the parent to update the value, you could instantiate the child component like so: <child :updateValue="updateValue"></child>. Then on the child you will have a corresponding prop: props: {updateValue: Function}, and in the template call the method when the input changes: <input #input="updateValue($event.target.value)">.

I don't know why, but I just successfully updated parent data with using data as object, :set & computed
Parent.vue
<!-- check inventory status - component -->
<CheckInventory :inventory="inventory"></CheckInventory>
data() {
return {
inventory: {
status: null
},
}
},
Child.vue
<div :set="checkInventory">
props: ['inventory'],
computed: {
checkInventory() {
this.inventory.status = "Out of stock";
return this.inventory.status;
},
}

his example will tell you how to pass input value to parent on submit button.
First define eventBus as new Vue.
//main.js
import Vue from 'vue';
export const eventBus = new Vue();
Pass your input value via Emit.
//Sender Page
import { eventBus } from "../main";
methods: {
//passing data via eventbus
resetSegmentbtn: function(InputValue) {
eventBus.$emit("resetAllSegment", InputValue);
}
}
//Receiver Page
import { eventBus } from "../main";
created() {
eventBus.$on("resetAllSegment", data => {
console.log(data);//fetching data
});
}

I think this will do the trick:
#change="$emit(variable)"

Intro
I was looking for sending data from parent to child (and back) in vue3 (I know the question was about vue2, but there are no references for vue3 on SO at the time).
Below is the working boilerplate result, pure "html + js", no packagers, modules, etc with few caveats I had, explained.
Notes:
Tnserting the child - line
<component-a :foo="bar" #newfooevent="bar = $event"></component-a>`
I bind parent.bar to child.foo using short-hand :foo="bar", same as v-bind:foo="bar". It passes data from parent to child through props.
Caveat: Event listener should be placed in the child component tag only!
That is the #newfooevent="bar = $event" part.
You cannot catch the signal in the <div id="app"> or anywhere else inside the parent.
Still, this is the parent's side of the universe, and here you can access all parent's data and extract the data from the child's signal to deal with it.
You can create app, and define component after it (the app.component("component-a", ...) part.
Caveat: there are no need in forward declaration of components, e.g. functions in C/C++. You can create app which uses the component, and define the component afterwards. I lost a lot of time looking for the way to declare it somehow - no need.
Here you can find a nice example of the v-model usage, and the code I used to sort things out: https://javascript.plainenglish.io/vue-3-custom-events-d2f310fe34c9
The example
<!DOCTYPE html>
<html lang="en">
<head>
<title>App</title>
<meta charset="utf-8" />
<script src="https://unpkg.com/vue#next"></script>
</head>
<body>
<div id="app">
<component-a :foo="bar" #newfooevent="bar = $event"></component-a>
<p>Parent copy of `bar`: {{ bar }}</p>
<button #click="bar=''">Clear</button>
</div>
<script>
const app = Vue.createApp({
data() {
return {
bar: "bar start value"
};
}
});
app.component("component-a", {
props: {
foo: String
},
template: `
<input
type="text"
:value="foo"
#input="$emit('newfooevent', $event.target.value)">
`
});
app.mount("#app");
</script>
</body>
</html>

There is another way of communicating data change from child to parent which uses provide-inject method. Parent component "provides" data or method for the child component, and this data or method is then "injected" into child component - but it can also be used for triggering a method in parent and passing it a parameter.
This approach can be especially useful when having a child component which happens to be embedded in multiple other components. Also, in a large project care must be taken not to lose overview of provide and inject usage.
Example of parent (top level) component App.vue using provide to give access to it's method updateParentValue (if method is provided and not data, provide is in form of a method):
<template>
<h2>App.vue, parentValue is: <em>{{ parentValue }}</em></h2>
<ChildComponent1 />
</template>
<script>
import ChildComponent1 from "./components/ChildComponent1.vue";
export default {
data() {
return {
parentValue: "",
};
},
components: {
ChildComponent1,
},
provide() {
return {
updateParent: this.updateParentValue,
};
},
methods: {
updateParentValue($value) {
this.parentValue = $value;
},
},
};
</script>
In this example component Component4.vue is in the "bottom", that is, App.vue contains Component1, Component1 contains Component2... until Component4 which actually utilizes inject to get access to parent method which is then invoked and a parameter $value is passed (just a random number here):
<template>
<div>
<h2>ChildComponent4.vue</h2>
<button #click="updateParent(Math.random())">
Update parent value in App.vue
</button>
</div>
</template>
<script>
export default {
inject: ["updateParent"],
};
</script>
Entire example is available here.
Vue.js documentation

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