Currently I have a vue-multiselect component which requires a v-model.
I want to wrap this component so that I can build one single-select component and one multi-select component.
While working on the single select component I encountered the following warning
[Vue warn]: Avoid mutating a prop directly since the value will be overwritten whenever the parent component re-renders. Instead, use a data or computed property based on the prop's value. Prop being mutated: "model"
They are right but in my case I really need to change the value from the parent (like I replace my single-select code with the vue-multiselect code) component and I also do not want this warning.
Here is the code for my component:
Vue.component('single-select', {
props: {
model: {
required: true
}
}
template: '<multiselect\n' +
' v-model="model"\n' +
...>\n' +
...
'</multiselect>'
});
One solution would be to pass a function as a model parameter and return the field from the parent but I really hope for a better solution.
Vue has a shortcut for 2 way binding called .sync modifier.
How it works in your case:
add .sync when you pass model as prop
<single-select :model.sync="..."></single-select>
emit an update:model in the child's input event
Vue.component('single-select', {
props: {
model: {
required: true
}
},
template: `<multiselect :value="model" #input="$emit('update:model', $event)"> </multiselect>`
});
Just give the internal model reference a different name, and the in the Vue component's data function map it manually:
Vue.component('single-select', {
props: {
model: {
required: true
}
},
data: function() {
return {
singleSelectModel: this.model
};
}
template: '<multiselect v-model="singleSelectModel"></multiselect>';
});
This is of course, assuming that you do not want to mutate the parent data, but simply making a copy of model and giving the child component the freedom to change it whenever it wants.
If what you want is to also update the parent data from the child, you will have to look into emitting events from the child and listening in the parent.
Related
I know we can pass data to child components via Props. But it is reactive in one-way data flow mode. If the value of the data is changed in Parent component, it also has effect (update) on props in Child component.
In my case, I don't want to get update on specific prop in Child component even if that data in the Parent component is changed. It is because Child component will only responsible to show the data. But the data in the Parent Component still has to be reactive in Parent Scope.
I've read some forum article that suggest to use like Json. I feel it is a little dirty way and the data in my case is just one string.
Is there anyways to achieve that kind of solution?
You could copy the reactive prop in the created hook of the child component. The copy would not be reactive e.g.
export default {
props: {
reactive: Object
},
data: () => ({
nonreactive: null
}),
created() {
this.nonreactive = Object.assign({}, this.reactive)
}
}
Note: the way you copy the reactive prop will depend on the data type, the way I've shown will work for objects.
Maybe u can check this one
VueJS render once into an element
use v-once on your child component
Use prop as data property in child component. please see the fiddle link:
link here
Vue.component('greeting', {
props: ['user'],
data:function(){
return {
newuser:this.user
}
},
template: '<h1>hi {{ newuser }}</h1>'
});
I am using a date picker component library and i want to watch when a property of that component changes.
I have tried this:
watch: {
'$refs.picker.popupVisible': {
handler (new_value) {
console.log('executed')
},
deep: true
}
}
Also this:
computed: {
picker () {
console.log(this.$refs.picker.popupVisible)
return this.$refs.picker.popupVisible
}
}
I know that the solution will be a vue.js hack because this is not the right way.If i had access to child component i would emit en event to parent but unfortunately i don't have.
I had a similar problem using a library which had some limitations.
Unfortunately, your watcher will not work.You have to use the function watcher to make this to work.And you have to use it inside the mounted hook.
mounted() {
this.$watch(
"$refs.picker.popupVisible",
(new_value, old_value) => {
//execute your code here
}
);
}
I also have an example. Please take a look here
What you can do is create a data object in parent component and include the date field in that data object and pass that data object to child component as props
<child :dateObj="dateObj"></child>
data: {
dateObj: {
date: ""
}
}
And in child component you can use the date field of that dateObj props. This is possible because Vue doesn't watch the property of Objects passed as props and we can modify them without Vue complaining in console.
Thus the changed date field is reflected in parent as well.
I've written a custom render function for a Vue Component, but when I set the "ref" property in the data object that is passed to the createElement function, nothing shows up in the $refs of the root vm (VueComponent)
Vue.component('sm-form-row', {
render: function (createElement) {
// Create the Row Div and append the columns
return createElement('div', {
class: {
'row': true
},
ref: 'some computed value'
});
}
});
What am I missing, the class is being applied correctly but the $refs keep showing empty.
The ref is beign applied and i made a fiddle to see it that it works.
But,if you want to add a reference to sm-form-row component then you have to add the ref attribute in the parent component.For example in parent component:
<sm-form-row ref="formRow" />
And in your parent component you can access it as:
this.$refs.formRow
Also you will be able to access the methods of the child component.For example if the child component has a method called myMethod you can access it in parent component like this:
this.$refs.formRow.myMethod
I have two components that are in a parent-child relationship. In the child select component I've defined a watcher for the currently selected value and I want the parent to get the updated value whenever it changes. I tried to use events but the parent can only listen to its own vm.
In the child component
watch: {
selected (value) {
this.$emit('selectedYearChange', value)
}
}
In the parent
mounted () {
this.$on('selectedYearChange', function (value) {
this.selectedYear = value
})
}
This obviously doesn't work because of the reason I mentioned above.
I wasn't able to find relevant examples in the documentation.
You can setup an event listener on the child component element itself where its used in the parent and pass it a method to be executed
//parent component
<div id="app>
<child-comp #selected-year-change='changeYear'></child-comp>
</div>
In your parent component use the method changeYear to change the value of `selectedYear'
methods:{
//you get the event as the parameter
changeYear(value){
this.selectedYear = value
}
}
See the fiddle
And avoid using camelCase for event names use kebab-case instead as HTML attributes are case-insensitive and may cause problems
html:
<Parent>
<Child #selected-year-change=HandleChange(data)></Child>
</Parent>
Javascript/Child Component:
watch: {
selected (value) {
this.$emit('selectedYearChange', value)
}
}
Javascript/Parent Component:
HandleChange: function(data){}
good luck. maybe work!
I'm using the vue-cli scaffold for webpack
My Vue component structure/heirarchy currently looks like the following:
App
PDF Template
Background
Dynamic Template Image
Static Template Image
Markdown
At the app level, I want a vuejs component method that can aggregate all of the child component's data into a single JSON object that can be sent off to the server.
Is there a way to access child component's data? Specifically, multiple layers deep?
If not, what is the best practice for passing down oberservable data/parameters, so that when it's modified by child components I have access to the new values? I'm trying to avoid hard dependencies between components, so as of right now, the only thing passed using component attributes are initialization values.
UPDATE:
Solid answers. Resources I found helpful after reviewing both answers:
Vuex and when to use it
Vuex alternative solution for smaller apps
In my child component, there are no buttons to emit changed data. It's a form with somewhat 5~10 inputs. the data will be submitted once you click the process button in another component. so, I can't emit every property when it's changing.
So, what I did,
In my parent component, I can access child's data from "ref"
e.g
<markdown ref="markdowndetails"></markdown>
<app-button #submit="process"></app-button>
// js
methods:{
process: function(){
// items is defined object inside data()
var markdowns = this.$refs.markdowndetails.items
}
}
Note: If you do this all over the application I suggest move to vuex instead.
For this kind of structure It's good to have some kind of Store.
VueJS provide solution for that, and It's called Vuex.If you are not ready to go with Vuex, you can create your own simple store.
Let's try with this
MarkdownStore.js
export default {
data: {
items: []
},
// Methods that you need, for e.g fetching data from server etc.
fetchData() {
// fetch logic
}
}
And now you can use those data everywhere, with importing this Store file
HomeView.vue
import MarkdownStore from '../stores/MarkdownStore'
export default {
data() {
sharedItems: MarkdownStore.data
},
created() {
MarkdownStore.fetchData()
}
}
So that's the basic flow that you could use, If you dont' want to go with Vuex.
what is the best practice for passing down oberservable data/parameters, so that when it's modified by child components I have access to the new values?
The flow of props is one way down, a child should never modify its props directly.
For a complex application, vuex is the solution, but for a simple case vuex is an overkill. Just like what #Belmin said, you can even use a plain JavaScript object for that, thanks to the reactivity system.
Another solution is using events. Vue has already implemented the EventEmitter interface, a child can use this.$emit('eventName', data) to communicate with its parent.
The parent will listen on the event like this: (#update is the shorthand of v-on:update)
<child :value="value" #update="onChildUpdate" />
and update the data in the event handler:
methods: {
onChildUpdate (newValue) {
this.value = newValue
}
}
Here is a simple example of custom events in Vue:
http://codepen.io/CodinCat/pen/ZBELjm?editors=1010
This is just parent-child communication, if a component needs to talk to its siblings, then you will need a global event bus, in Vue.js, you can just use an empty Vue instance:
const bus = new Vue()
// In component A
bus.$on('somethingUpdated', data => { ... })
// In component B
bus.$emit('somethingUpdated', newData)
you can meke ref to child component and use it as this
this.$refs.refComponentName.$data
parent-component
<template>
<section>
<childComponent ref="nameOfRef" />
</section>
</template>
methods: {
save() {
let Data = this.$refs.nameOfRef.$data;
}
},
In my case I have a registration form that I've broken down into components.
As suggested above I used $refs, In my parent I have for example:
In Template:
<Personal ref="personal" />
Script - Parent Component
export default {
components: {
Personal,
Employment
},
data() {
return {
personal: null,
education: null
}
},
mounted: function(){
this.personal = this.$refs.personal.model
this.education = this.$refs.education.model
}
}
This works well as the data is reactive.