I have a simple component that uses mixin that's shared across multiple components with similar functionality.
When I run it I seem to be getting
Property or method "activeClass" is not defined on the instance but
referenced during render.
Here's my mixin
<script>
export default {
data() {
return {
opened: false,
identity: ''
}
},
computed: {
activeClass() {
return {
active: this.opened
};
}
},
created() {
window.EventHandler.listen(this.identity + '-toggled', opened => this.opened = opened);
},
methods: {
toggle() {
window.EventHandler.fire('toggle-' + this.identity);
}
}
}
</script>
and my component
<template>
<span class="pointer" :class="activeClass" #click="toggle"><i class="fas fa-search"></i></span>
</template>
<script>
import Trigger from '../../mixins/Trigger';
export default {
data() {
return {
mixins: [Trigger],
data() {
return {
identity: 'language'
}
}
}
}
}
</script>
For some reason I cannot seem to be able to access activeClass computed property from within the component. Any idea why is this happening?
Try to move mixin to components main scope. Not in data function rerurn
Related
When I maximize window via drag titlebar electron emits 'maximize' event. I want to call 'maximize' method that exist inside 'export default' scope. How can I call?
<template>
<div class="window-titlebar">
<div class="title">{{ title }}</div>
</div>
</template>
<script>
const electron = require('electron');
import { ipcRenderer } from 'electron';
export default {
name: 'window-titlebar',
data() {
return {
title: false
}
},
methods: {
maximize: function() {
this.title = true;
}
}
}
ipcRenderer.on('maximize', () => {
// I want to call 'maximize' method here
})
</script>
It would be better to register the event handler on the component itself, that way you can tie the existence of the event handler to the lifetime of the component and the event handler will execute within the context of the component instance.
export default {
name: 'window-titlebar',
data() {
return {
title: false
}
},
created() {
ipcRenderer.on('maximize', this.onMaximize)
},
destroyed() {
ipcRenderer.off('maximize', this.onMaximize)
},
methods: {
onMaximize() {
this.title = true
}
}
}
In the parent, define a reference
<WindowTitlebar ref="titlebar" />
Then call the method via $refs
this.$refs.titlebar.maximize();
I am trying to send this.TC from typing.js to ending-page.js which are sibling components. Emits and event hubs not working. But emit from typing.js to parent works as I want. (There will be only one more call in this app, so i don't want use Vuex if it isnt necessary for this - i want to do it with simple emits ) Here's my code:
Parent:
<template>
<div id = "app">
<typing v-if = "DynamicComponent === 'typing'" />
<ending_page v-else-if = "DynamicComponent === 'ending_page'" />
</div>
</template>
<script>
/* Importing siblings components to parent component */
import typing from './components/typing/index.vue'
import ending_page from './components/ending-page/index.vue'
export default {
name: 'app',
components: {
typing,
ending_page
},
data() {
return {
DynamicComponent: "typing",
};
},
methods: {
updateDynamicComponent: function(evt, data){
this.DynamicComponent = evt;
},
},
};
</script>
typing.js:
import { eventBus } from "../../main";
export default {
name: 'app',
components: {
},
data() {
return {
/* Text what is in input. If you write this.input = "sometext" input text will change (It just works from JS to HTML and from HTML to JS) */
input: "",
/* Object of TypingCore.js */
TC: "somedata",
/* Timer obejct */
timer: null,
is_started: false,
style_preferences: null,
};
},
ICallThisFunctionWhenIWantToEmitSomething: function(evt) {
/* Sending data to ending_page component */
this.$root.$emit('eventname', 'somedata');
/* Calling parent to ChangeDynamicComponent && sending TC.data what will be given to ending_page (I think it looks better with one syntax here) */
this.$emit('myEvent', 'ending_page', this.TC.data);
}
},
};
ending-page.js:
import { eventBus } from "../../main";
export default {
name: 'ending-page',
components: {},
data () {
return {
data: "nothing",
}
},
computed: {
},
props: {
},
methods: {
},
/* I know arrow functions etc but i was trying everyting */
created: function () {
this.$root.$on('eventname', function (data) {
console.log(data)
this.title = data
this.$nextTick()
})
}
}
It is an example of how to share data between siblings components.
Children components emits events to parent. Parent components send data to children.
So, the parent has the property title shared between the children. When typing emits
the input event the directive v-modelcapture it an set the value on parent.
Ref:
https://v2.vuejs.org/v2/guide/components-props.html#One-Way-Data-Flow
https://v2.vuejs.org/v2/guide/components.html#Using-v-model-on-Components
https://benjaminlistwon.com/blog/data-flow-in-vue-and-vuex/
Vue.component('typing', {
props: {
value: ''
},
template: '<button #click="emit">Click to change</button>',
methods: {
emit() {
this.$emit('input', `changed on ${Date.now()}`);
}
}
});
Vue.component('ending-page', {
props: {
title: ''
},
template: '<div>{{ title }}</div>',
});
var app = new Vue({
el: '#app',
data() {
return {
title: 'unchanged',
};
},
});
<script src="https://cdnjs.cloudflare.com/ajax/libs/vue/2.5.17/vue.js"></script>
<div id="app">
<typing v-model="title"></typing>
<ending-page :title="title"></ending-page>
</div>
One can try communication using vuex,
the data you want to share make it on this.$store.state or if recalling for functions use mutation(sync functions) and actions(async functions)
https://vuex.vuejs.org/
I like what Jeffrey Way suggested once, just create a global events object (which accidentally can be another Vue instance) and then use that as an event bus for any global communication.
window.eventBus = new Vue();
// in components that emit:
eventBus.$emit('event', data);
// in components that listen
eventBus.$on('event');
I'm trying to create a "Dropdown List" component. This component should take in a title and a route. I'm having trouble setting up the javascript for this component within the parent. Here is what I'm working with.
PARENT COMPONENT:
<template>
<UserDropdownList v-for="item in items"></UserDropdownList>
</template>
<script>
import SignUp from "../forms/SignUp";
import SignIn from "../forms/SignIn";
import UserDropdownList from "./UserDropdownList";
import { mixin as clickaway } from 'vue-clickaway';
export default {
mixins: [ clickaway ],
components: {
SignUp,
SignIn,
UserDropdownList
},
data: function () {
return {
items: [
{ title: 'Profile', route: "/profile" },
{ title: 'Users', route: "/users" }
]
}
},
computed: {
isLoggedIn () {
return this.$store.getters.isLoggedIn
},
userName () {
return this.$store.getters.currentUser.userName
},
isDropdownOpen () {
return this.$store.getters.dropdownIsOpen
}
},
methods: {
signOut: function(event) {
this.$store.commit("CLOSE_DROPDOWN");
this.$store.commit("LOGOUT");
this.$router.push('/');
},
openDropdown: function() {
if (event.target.id != "button") {
this.$store.commit("OPEN_DROPDOWN");
}
},
closeDropdown: function() {
this.$store.commit("CLOSE_DROPDOWN");
}
}
}
</script>
USER DROPDOWN LIST
<template>
<li v-on:click="closeDropdown"><router-link to={{ item.route }} id="button">{{ item.title }}</router-link></li>
</template>
<script>
export default {
}
</script>
<style>
</style>
ERRORS:
Property or method "item" is not defined on the instance but referenced during render. Make sure that this property is reactive, either in the data option, or for class-based components, by initializing the property.
Error in render: "TypeError: Cannot read property 'title' of undefined"
Anyone understand what I am doing wrong?
you didn't pass item as a props to UserDropdownList
first, pass item as a prop to UserDropdownList
<template>
<UserDropdownList v-for="item in items" v-bind:item="item"></UserDropdownList>
</template>
then, setup UserDropdownList to receive item prop
export default {
props: ['item']
}
I have a simple application which need to render 2 components dynamically.
Component A - needs to have onClick event.
Component B - needs to have onChange event.
How is it possible to dynamically attach different events to component A/B?
<template>
<component v-bind:is="currentView">
</component>
</template>
<script>
import A from '../components/a.vue'
import B from '../components/b.vue'
export default {
data: function () {
return {
currentView: A
}
},
components: { A, B }
}
</script>
Here is a solution for a little more complicated and realistic use case. In this use case you have to render multiple different components using v-for.
The parent component passes an array of components to create-components. create-components will use v-for on this array, and display all those components with the correct event.
I'm using a custom directive custom-events to achieve this behavior.
parent:
<template>
<div class="parent">
<create-components :components="components"></create-components>
</div>
</template>
<script>
import CreateComponents from '#/components/CreateComponents'
import ComponentA from '#/components/ComponentA'
import ComponentB from '#/components/ComponentB'
export default {
name: 'parent',
data() {
return {
components: [
{
is: ComponentA,
events: {
"change":this.componentA_onChange.bind(this)
}
},
{
is: ComponentB,
events: {
"click":this.componentB_onClick.bind(this)
}
}
]
}
},
methods: {
componentA_onChange() {
alert('componentA_onChange');
},
componentB_onClick() {
alert('componentB_onClick');
}
},
components: { CreateComponents }
};
</script>
create-components:
<template>
<div class="create-components">
<div v-for="(component, componentIndex) in components">
<component v-bind:is="component.is" v-custom-events="component.events"></component>
</div>
</div>
</template>
<script>
export default {
name: 'create-components',
props: {
components: {
type: Array
}
},
directives: {
CustomEvents: {
bind: function (el, binding, vnode) {
let allEvents = binding.value;
if(typeof allEvents !== "undefined"){
let allEventsName = Object.keys(binding.value);
allEventsName.forEach(function(event) {
vnode.componentInstance.$on(event, (eventData) => {
allEvents[event](eventData);
});
});
}
},
unbind: function (el, binding, vnode) {
vnode.componentInstance.$off();
}
}
}
}
</script>
You don't have to dynamically add them.
<component v-bind:is="currentView" #click="onClick" #change="onChange">
If you want to be careful you can bail in the handler of the currentView is not correct.
methods: {
onClick(){
if (this.currentView != A) return
// handle click
},
onChange(){
if (this.currentView != B) return
// handle change
}
}
Context
In Vue 2.0 the documentation and others clearly indicate that communication from parent to child happens via props.
Question
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).
Example
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.
Vue 3 Composition API
Create a ref for the child component, assign it in the template, and use the <ref>.value to call the child component directly.
<script setup>
import {ref} from 'vue';
const childComponentRef = ref(null);
function click() {
// `childComponentRef.value` accesses the component instance
childComponentRef.value.doSomething(2.0);
}
</script>
<template>
<div>
<child-component ref="childComponentRef" />
<button #click="click">Click me</button>
</div>
</template>
Couple things to note-
If your child component is using <script setup>, you'll need to declare public methods (e.g. doSomething above) using defineExpose.
If you're using Typescript, details of how to type annotate this are here.
Vue 3 Options API / Vue 2
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 3 docs on component refs or Vue 2 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/
A simple decoupled way to call methods on child components is by emitting a handler from the child and then invoking it from parent.
var Child = {
template: '<div>{{value}}</div>',
data: function () {
return {
value: 0
};
},
methods: {
setValue(value) {
this.value = value;
}
},
created() {
this.$emit('handler', this.setValue);
}
}
new Vue({
el: '#app',
components: {
'my-component': Child
},
methods: {
setValueHandler(fn) {
this.setter = fn
},
click() {
this.setter(70)
}
}
})
<script src="https://cdn.jsdelivr.net/npm/vue#2.5.17/dist/vue.js"></script>
<div id="app">
<my-component #handler="setValueHandler"></my-component>
<button #click="click">Click</button>
</div>
The parent keeps track of the child handler functions and calls whenever necessary.
Did not like the event-bus approach using $on bindings in the child during create. Why? Subsequent create calls (I'm using vue-router) bind the message handler more than once--leading to multiple responses per message.
The orthodox solution of passing props down from parent to child and putting a property watcher in the child worked a little better. Only problem being that the child can only act on a value transition. Passing the same message multiple times needs some kind of bookkeeping to force a transition so the child can pick up the change.
I've found that if I wrap the message in an array, it will always trigger the child watcher--even if the value remains the same.
Parent:
{
data: function() {
msgChild: null,
},
methods: {
mMessageDoIt: function() {
this.msgChild = ['doIt'];
}
}
...
}
Child:
{
props: ['msgChild'],
watch: {
'msgChild': function(arMsg) {
console.log(arMsg[0]);
}
}
}
HTML:
<parent>
<child v-bind="{ 'msgChild': msgChild }"></child>
</parent>
The below example is self explainatory. where refs and events can be used to call function from and to parent and child.
// PARENT
<template>
<parent>
<child
#onChange="childCallBack"
ref="childRef"
:data="moduleData"
/>
<button #click="callChild">Call Method in child</button>
</parent>
</template>
<script>
export default {
methods: {
callChild() {
this.$refs.childRef.childMethod('Hi from parent');
},
childCallBack(message) {
console.log('message from child', message);
}
}
};
</script>
// CHILD
<template>
<child>
<button #click="callParent">Call Parent</button>
</child>
</template>
<script>
export default {
methods: {
callParent() {
this.$emit('onChange', 'hi from child');
},
childMethod(message) {
console.log('message from parent', message);
}
}
}
</script>
If you have time, use Vuex store for watching variables (aka state) or trigger (aka dispatch) an action directly.
Calling child component in parent
<component :is="my_component" ref="my_comp"></component>
<v-btn #click="$refs.my_comp.alertme"></v-btn>
in Child component
mycomp.vue
methods:{
alertme(){
alert("alert")
}
}
I think we should to have a consideration about the necessity of parent to use the child’s methods.In fact,parents needn’t to concern the method of child,but can treat the child component as a FSA(finite state machine).Parents component to control the state of child component.So the solution to watch the status change or just use the compute function is enough
you can use key to reload child component using key
<component :is="child1" :filter="filter" :key="componentKey"></component>
If you want to reload component with new filter, if button click filter the child component
reloadData() {
this.filter = ['filter1','filter2']
this.componentKey += 1;
},
and use the filter to trigger the function
You can simulate sending event to child by toggling a boolean prop in parent.
Parent code :
...
<child :event="event">
...
export default {
data() {
event: false
},
methods: {
simulateEmitEventToChild() {
this.event = !this.event;
},
handleExample() {
this.simulateEmitEventToChild();
}
}
}
Child code :
export default {
props: {
event: {
type: Boolean
}
},
watch: {
event: function(value) {
console.log("parent event");
}
}
}