The following code has been written to handle an event after a button click
var MainTable = Vue.extend({
template: "<ul>" +
"<li v-for='(set,index) in settings'>" +
"{{index}}) " +
"{{set.title}}" +
"<button #click='changeSetting(index)'> Info </button>" +
"</li>" +
"</ul>",
data: function() {
return data;
}
});
Vue.component("main-table", MainTable);
data.settingsSelected = {};
var app = new Vue({
el: "#settings",
data: data,
methods: {
changeSetting: function(index) {
data.settingsSelected = data.settings[index];
}
}
});
But the following error occurred:
[Vue warn]: Property or method "changeSetting" is not defined on the instance but referenced during render. Make sure to declare reactive data properties in the data option. (found in <MainTable>)
Problem
[Vue warn]: Property or method "changeSetting" is not defined on the instance but referenced during render. Make sure to declare reactive data properties in the data option. (found in <MainTable>)
The error is occurring because the changeSetting method is being referenced in the MainTable component here:
"<button #click='changeSetting(index)'> Info </button>" +
However the changeSetting method is not defined in the MainTable component. It is being defined in the root component here:
var app = new Vue({
el: "#settings",
data: data,
methods: {
changeSetting: function(index) {
data.settingsSelected = data.settings[index];
}
}
});
What needs to be remembered is that properties and methods can only be referenced in the scope where they are defined.
Everything in the parent template is compiled in parent scope; everything in the child template is compiled in child scope.
You can read more about component compilation scope in Vue's documentation.
What can I do about it?
So far there has been a lot of talk about defining things in the correct scope so the fix is just to move the changeSetting definition into the MainTable component?
It seems that simple but here's what I recommend.
You'd probably want your MainTable component to be a dumb/presentational component. (Here is something to read if you don't know what it is but a tl;dr is that the component is just responsible for rendering something – no logic). The smart/container element is responsible for the logic – in the example given in your question the root component would be the smart/container component. With this architecture you can use Vue's parent-child communication methods for the components to interact. You pass down the data for MainTable via props and emit user actions from MainTable to its parent via events. It might look something like this:
Vue.component('main-table', {
template: "<ul>" +
"<li v-for='(set, index) in settings'>" +
"{{index}}) " +
"{{set.title}}" +
"<button #click='changeSetting(index)'> Info </button>" +
"</li>" +
"</ul>",
props: ['settings'],
methods: {
changeSetting(value) {
this.$emit('change', value);
},
},
});
var app = new Vue({
el: '#settings',
template: '<main-table :settings="data.settings" #change="changeSetting"></main-table>',
data: data,
methods: {
changeSetting(value) {
// Handle changeSetting
},
},
}),
The above should be enough to give you a good idea of what to do and kickstart resolving your issue.
Should anybody land with the same silly problem I had, make sure your component has the 'data' property spelled correctly. (eg. data, and not date)
<template>
<span>{{name}}</span>
</template>
<script>
export default {
name: "MyComponent",
data() {
return {
name: ""
};
}
</script>
In my case the reason was, I only forgot the closing
</script>
tag.
But that caused the same error message.
If you're experiencing this problem, check to make sure you don't have
methods: {
...
}
or
computed: {
...
}
declared twice
It's probably caused by spelling error
I got a typo at script closing tag
</sscript>
Remember to return the property
Another reason of seeing the Property "search" was accessed during render but is not defined on instance is when you forget to return the variable in the setup(){} function
So remember to add the return statement at the end:
export default {
setup(){
const search = ref('')
//Whatever code
return {search}
}
}
Note: I'm using the Composition API
Adding my bit as well, should anybody struggle like me, notice that methods is a case-sensitive word:
<template>
<span>{{name}}</span>
</template>
<script>
export default {
name: "MyComponent",
Methods: {
name() {return '';}
}
</script>
'Methods' should be 'methods'
If you use two times vue instance. Then it will give you this error. For example in app.js and your own script tag in view file. Just use one time
const app = new Vue({
el: '#app',
});
I got this error when I tried assigning a component property to a state property during instantiation
export default {
props: ['value1'],
data() {
return {
value2: this.value1 // throws the error
}
},
created(){
this.value2 = this.value1 // safe
}
}
My issue was I was placing the methods inside my data object. just format it like this and it'll work nicely.
<script>
module.exports = {
data: () => {
return {
name: ""
}
},
methods: {
myFunc() {
// code
}
}
}
</script>
In my case, I wrote it as "method" instead of "methods". So stupid. Wasted around 1 hour.
Some common cases of this error
Make sure your component has the data property spelled correctly
Make sure your template is bot defined within another component’s template.
Make sure you defined the variable inside data object
Make sure your router name in string
Get some more sollution
It is most likely a spelling error of reserved vuejs variables. I got here because I misspelled computed: and vuejs would not recognize my computed property variables. So if you have an error like this, check your spelling first!
I had two methods: in the <script>, goes to show, that you can spend hours looking for something that was such a simple mistake.
if you have any props or imported variables (from external .js file) make sure to set them properly using created like this;
make sure to init those vars:
import { var1, var2} from './constants'
//or
export default {
data(){
return {
var1: 0,
var2: 0,
var3: 0,
},
},
props: ['var3'],
created(){
this.var1 = var1;
this.var2 = var2;
this.var3 = var3;
}
In my case it was a property that gave me the error, the correct writing and still gave me the error in the console. I searched so much and nothing worked for me, until I gave him Ctrl + F5 and Voilá! error was removed. :'v
Look twice the warning : Property _____ was accessed during render but is not defined on instance.
So you have to define it ... in the data function for example which commonly instantiate variables in a Vuejs app. and, it was my case and that way the problem has been fixed.
That's all folk's !
In my case, I forgot to add the return keyword:
computed: {
image(){
this.productVariants[this.selectedVariant].image;
},
inStock(){
this.productVariants[this.selectedVariant].quantity;
}
}
Change to:
computed: {
image(){
return this.productVariants[this.selectedVariant].image;
},
inStock(){
return this.productVariants[this.selectedVariant].quantity;
}
}
In my case due to router name not in string:
:to="{name: route-name, params: {id:data.id}}"
change to router name in string:
:to="{name: 'router-name', params: {id:data.id}}"
In my case I was trying to pass a hard coded text value to another component with:
ChildComponent(:displayMode="formMode")
when it should be:
ChildComponent(:displayMode="'formMode'")
note the single quotes to indicate text instead of calling a local var inside the component.
If you're using the Vue3 <script setup> style, make sure you've actually specified setup in the opening script tag:
<script setup>
I had lapsed into old habits and only created a block with <script>, but it took a while to notice it.
https://v3.vuejs.org/api/sfc-script-setup.html
Although some answers here maybe great, none helped my case (which is very similar to OP's error message).
This error needed fixing because even though my components rendered with their data (pulled from API), when deployed to firebase hosting, it did not render some of my components (the components that rely on data).
To fix it (and given you followed the suggestions in the accepted answer), in the Parent component (the ones pulling data and passing to child component), I did:
// pulled data in this life cycle hook, saving it to my store
created() {
FetchData.getProfile()
.then(myProfile => {
const mp = myProfile.data;
console.log(mp)
this.$store.dispatch('dispatchMyProfile', mp)
this.propsToPass = mp;
})
.catch(error => {
console.log('There was an error:', error.response)
})
}
// called my store here
computed: {
menu() {
return this.$store.state['myProfile'].profile
}
},
// then in my template, I pass this "menu" method in child component
<LeftPanel :data="menu" />
This cleared that error away. I deployed it again to firebase hosting, and voila!
Hope this bit helps you.
It seems there are many scenarios that can trigger this error. Here's another one which I just resolved.
I had the variable actionRequiredCount declared in the data section, but I failed to capitalize the C in Count when passing the variable as a params to a component.
Here the variable is correct:
data: () => {
return{
actionRequiredCount: ''
}
}
In my template it was incorrect (notd the no caps c in "count"):
<MyCustomModule :actionRequiredCount="actionRequiredcount"/>
Hope this helps someone.
Most people do have an error here because of:
a typo or something that they forgot to declare/use
the opposite, did it in several places
To avoid the typo issues, I recommend always using Vue VSCode Snippets so that you don't write anything by hand by rather use vbase, vdata, vmethod and get those parts generated for you.
Here are the ones for Vue3.
You can of course also create your own snippets by doing the following.
Also make sure that you're properly writing all the correct names as shown here, here is a list:
data
props
computed
methods
watch
emits
expose
As for the second part, I usually recommend either searching the given keyword in your codebase. So like cmd + f + changeSetting in OP's case to see if it's missing a declaration somewhere in data, methods or alike.
Or even better, use an ESlint configuration so that you will be warned in case you have any kind of issues in your codebase.
Here is how to achieve such setup with a Nuxt project + ESlint + Prettier for the most efficient way to prevent bad practices while still getting a fast formatting!
One other common scenario is:
You have a component (child) extending another component (parent)
You have a property or a method xyz defined under methods or computed on the parent component.
Your are trying to use parent's xyz, but your child component defines its own methods or computed
Sample code with the problem
// PARENT COMPONENT
export default {
computed() {
abc() {},
xyz() {} // <= needs to be used in child component
},
...
}
// CHILD COMPONENT
export default {
extends: myParentComponent,
computed() {
childProprty1() {},
childProprty2() {}
}
}
The solution
In this case you will need to redefine your xyz computed property under computed
Solution 1:
Redefine xyz and copy the code from the parent component
// CHILD COMPONENT
export default {
extends: myParentComponent,
computed() {
xyz() {
// do something cool!
},
childProprty1() {},
childProprty2() {}
}
}
Solution 2
Redefine xyz property reusing parent component code (no code redundancy)
// CHILD COMPONENT
export default {
extends: myParentComponent,
computed() {
xyz() {
return this.$parent.$options.computed.xyz
},
childProprty1() {},
childProprty2() {}
}
}
For me it happened because I wrote method: instead of methods: (plural). It's a silly mistake but it can happen :)
In my case it was the methods: { } I had put the } before my method functions so for example I had it like this methods: { function , function }, function, function so some of the functions that were out of the curly braces were not included inside the methods function.
In the simplified example below I demonstrate my problem:
I have a for-loop that asynchronously updates myItems.
I want to be able and update accordingly selectableItems by using this.$el.querySelector('selectable-item').
<template>
<div>
<p>selectableItems: {{selectableItems}}</p>
<div v-for="item in myItems" class="selectable-item">item</div>
</div>
</template>
<script>
export default {
name: 'MyComponent',
data() {
return {
myItems: [],
selectableItems: [],
}
},
created(){
// Populate myItems with a delay
self = this
setTimeout(function() {
self.myItems = [1, 2, 3]
}, 1000);
},
mounted(){
// Fetch some of myItems based on a class
this.selectableItems = this.$el.querySelectorAll('.selectable-item')
},
}
</script>
<style scoped lang="scss">
</style>
I've tried many different things I've found online; TickNext, computed, updated, etc. I think I'm doing something fundamentally wrong. But it is important for my case to be able and select DOM elements by a class.
Any help is deeply appreciated.
Updated: More context
Some people asked me for the bigger picture so I give a bit more info here.
Currently I have a big Vue component where the user is able to select elements. I am trying to factor out all this user interaction into a mixin so I can re-use it in other places of my code.
To make re-usability easy I need to be able and simply add a class selectable to any HTML tag in the template. That's the interface and then the mixin does all the magic and populates selectedElements depending on user interaction.
That's why it is important to avoid refs, etc. since then too much logic leaks everywhere and beats the purpose of making the mixin re-usable. Unless I'm missing something.
OK, after trying many different things I've managed to solve this by using a non-reactive intermediate variable. This means that I can't use the variable in a template but that is fine.
export default {
..
// NOT reactive so you can't just use it in your templates.
_selectableItems: [],
updated(){
self._selectableItems = self.$el.querySelectorAll('.selectable-item')
},
..
}
I have a vue date component that is composed of a vue-flatpickr-component. When I pass config options in as props, of course, they work as expected, however, if want to change one of the config options which should be possible, it won't propagate down. I'm not a Vue guru, any advice would be helpful.
I'm using a page component in a Laravel app, it shouldn't be relevant, however, just in case someone answers with vuex or vue-router, those won't work here.
Here are the form elements in play from page.vue:
<material-select
name="specialist"
label="Specialist"
default-text="CHOOSE HOMEVISIT SPECIALIST"
:options="staffMembers"
v-model="form.specialist"
:validation-error="form.errors.first('specialist')"
class="mb-4"
></material-select>
<div class="w-1/2">
<material-date
label="Appointment date"
name="appointment_date"
v-model="form.appointment_date"
:validation-error="form.errors.first('appointment_date')"
class="mb-4"
:external-options="{
enable: this.appointmentDates,
}"
></material-date>
<pre>{{ this.appointmentDates }}</pre>
</div>
Here is the computed property driving the config change:
computed: {
appointmentDates(){
if(this.form.specialist !== null){
return this.availableDates[this.form.specialist - 1]
}
return []
},
When a different home visit specialist is chosen, it will update with Vue's reactivity.
I have a computed property changing the config options. Here are the props data and the relevant computed property from the MaterialDate.vue file:
import flatPickr from 'vue-flatpickr-component';
import 'flatpickr/dist/flatpickr.css';
export default {
components: {
flatPickr
},
props: {
value: String,
label: String,
validationError: String,
name: {required:true},
optional: {
default: false
},
externalOptions: {}
},
data() {
return {
defaults: {disableMobile: true,},
options: this.externalOptions
}
},
computed: {
config(){
return Object.assign({}, this.defaults, this.options)
},
This will of course never update the enabled dates option because the prop is immutable, I need to get access to the set(option, value) section of the wrapped by vue-flatpickr-component. However, my Vue kungfu is not really strong enough to source dive it to see how I might access it and programatically call set('enabled', [new dates]).
Sometimes, you shouldn't code when you are tired :) But Hopefully this will help someone at some point. I was over thinking this. Data is passed down through props, and if controlling data changes it has to be reflected in the propagated data. Much like v-model with it's value prop.
So instead of binding the config object on this.options which doesn't stay hooked to it's prop value that it was initialized from, the computed function should be calculated from the prop which will change based on the new passed in options prop.
so simply change the computed function to:
computed: {
config(){
return Object.assign({}, this.defaults, this. externalOptions)
},
and remove the data element.
... Elementary
Sorry for the cheese it's late and I feel relieved.
ok so I've learned that I'm not supposed to call a child's method but pass it props instead.
I've got (parent) :
<template>
<div id="main">
<Header :title ="title"/>
<router-view/>
<LateralMenu/>
</div>
</template>
<script>
export default {
name: 'app'
data: function () {
return {
title: true
}
},
methods: {
hideTitle: function () {
this.title = false
console.log(this.title)
},
showTitle: function () {
this.title = true
console.log(this.title)
}
}
}
</script>
and (child) :
<script>
export default {
name: 'Header',
props: ['title'],
created () {
console.log(this.title)
},
methods: {
}
}
</script>
the first console logs (inside the parent) print correctly on each method but the second console log within the child stays true all the time. I got this from : Pass data from parent to child component in vue.js
inside what method does the console.log need to be to be printed everytime the methods in the parent are triggered?
(this is why I wanted to go for method-calling, originally, by going with variables instead, we're potentially omitting valuable parts of the process such as optimization and a "when" for the execution(s!!) of our code. pontetally being the key word here, don't blow up on me, keep in mind that I'm learning.)
OLD:
I've browsed the web and I know there a a million different answers
and my point is with the latest version of vue none of those millions
of answers work.
either everything is deprecated or it just doesn't apply but I need a
solution.
How do you call a child method?
I have a 1 component = 1 file setup.
DOM is declared inside a <template> tag javascript is written inside
a <script> tag. I'm going off of vue-cli scaffolding.
latest method I've tried is #emit (sometimes paired with an #on
sometimes not) doesn't work :
child :
<script>
export default {
name: 'Header',
created () {
this.$on('hideTitlefinal', this.hideTitlefinal)
},
methods: {
hideTitlefinal: function () {
console.log('hideeeee')
},
showTitlefinal: function () {
console.log('shwowwww')
}
}
}
</script>
parent :
<template>
<div id="main">
<Header v-on:hideTitle="hideTitlefinal" v-on:showTitle="showTitlefinal"/>
<router-view/>
<LateralMenu/>
</div>
</template>
<script>
export default {
methods: {
hideTitle: function () {
this.$emit('hideTitle')
},
showTitle: function () {
this.$emit('showTitle')
}
}
}
</script>
console :
Uncaught TypeError: this.$emit is not a function
at Object.showTitle (Main.vue?1785:74)
at VueComponent.showTitle (LateralMenu.vue?c2ae:113)
at boundFn (vue.esm.js?efeb:186)
at invoker (vue.esm.js?efeb:1943)
at HTMLDivElement.fn._withTask.fn._withTask (vue.esm.js?efeb:1778)
Please don't do this. You're thinking in terms of events. When x happens, do y. That's sooo jquery 2005 man. Vue still has all that stuff, but we're being invited to think in terms of a view model...
You want your state in a variable, in window scope, and you want reactive pipes linking your vue stuff to your state object. To toggle visibility, use a dynamic class binding, or v-if. Then think about how to represent your state. It could be as simple as having a property like store.titleVisible. But, you want to 'normalize' your store, and avoid relationships between items of state. So if title visibility really depends on something higher up, like an editMode or something, then just put the higher-up thing in the store, then create computed properties if you need them.
The goal is that you don't care when things happen. You just define the relationships between the markup and the store, then let Vue take care of it. The docs will tell you to use props for parent=>child and $emit for child=>parent communication. Truth is you don't need this until you have multiple instances of a component, or reusable components. Vue stuff talks to a store, not to other vue stuff. For single-use components, as for your root Vue, just use the data:.
Whenever you find yourself writing show/hide methods, you're doing it wrong. It's intuitive (because it's procedural), but you'll quickly appreciate how much better the MVVM approach is.
I'm a beginner, this is probably more of a javascript problem than vue but anyway:
there a plugin for spreadsheet named handsontable and in the normal use you make the table by doing this
hot = new Handsontable(container, {option})
and then you can use the method like hot.loadData() etc..
To use handsontable with vuejs, there a wrapper we can find here https://github.com/handsontable/vue-handsontable-official. With the wrapper you make a table like this :
<template>
<div id="hot-preview">
<HotTable :root="root" :settings="hotSettings"></HotTable>
</div>
</template>
<script>
import HotTable from 'vue-handsontable-official';
import Vue from 'vue';
export default {
data: function() {
return {
root: 'test-hot',
hotSettings: {
data: [['sample', 'data']],
colHeaders: true
}
};
},
components: {
HotTable
}
mounted () {
localforage.config({
driver: localforage.INDEXEDDB,
name: 'matchlist-database'
})
localforage.getItem('DB').then(function (value) {
console.log('then i fetch the DB: ' + JSON.stringify(value))
if (value !== 'null') {
console.log('dB contain something')
**root**.loadData(value)
}
</script>
So it work fine when i give an array but to load the data from a DB you must call the handsontable method hot.loadData(data).
i cannot find how to call this method in vuejs i always get the error
TypeError: root.loadData is not a function
i tried with all i could think of instead of root ex: HotTable.loadData(value)
but to no avail
Can someone point me out how i would call handsontable methods from the vuejs wrapper. Or point me out what kind of reading i should do to understand my mistake. Thank a lot
There are two problems here, not bad ones :)
1st problem:
If you want to refer to your data inside Vue's methods/computed properties/watchers/lifecycle events, you should use the this keyword. If you have data: function() { return { root: "root-value" }} and you would like to console.log that "root-value" string, you should write console.log(this.root) inside your mounted handler.
If you had something like:
data: function() {
return {
hot = new Handsontable(container, {option})
....
};
You could call hot.loadData() like so:
mounted() {
this.hot.loadData();
...
}
So this refers to the Vue instance which exposes your data properties.
2nd problem:
If I understand the component wrapper correctly, you are supposed to pass data to it as props, not call any Handsontable methods directly.
<HotTable :root="root" :settings="hotSettings"></HotTable>
This means that Vue passes whatever you have as root in your data to the HotTable component. It also passes whatever you have as settings in your data. In the example, HotTable receives these:
root: 'test-hot',
hotSettings: {
data: [['sample', 'data']],
colHeaders: true
}
Now if you want to change/update/modify/add data that should be passed to the HotTable component, you should update your data in the Vue instance. You should do something like this.hotSettings = something new and this.root = something else and the HotTable component would receive those.
To understand what's really happnening with the HotTable, read all of the component documentation. Really. You will save lots of time if you read through the documentation. It all makes sense after that!
https://v2.vuejs.org/v2/guide/components.html