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.
I'm trying to use Vue Chart.js to implement a chart selector to visualise various data.
Structure of application:
ChartPicker.vue (allow user to pick chart, create data, use dynamic component key to re-render component)
ChartWrapper.vue (receives props and passes them on, creates mixin for dynamic chart type)
ChartRender.vue (simply renders chart)
In the chart render component you usually you need to do 'extends: Bar', 'extends: Line' etc, therefore, requiring a ChartRender component type for each chart type. I found a neat solution that passes in the chart type to the chart mixins, then the final chart render makes no reference to chart type (not quite clear how this works even after looking at vue-chart.js code). This is the example I based my code on (it has no chart type selection):
https://codesandbox.io/s/vue-template-original-1czfi
So, I tried to extend functionality of that example to add a chart selector. It's working to an extent on chart type change: data changes, components re-render but the chart type doesn't change (even though it's being passed to the mixin dynamically)
I have a running example here:
https://codesandbox.io/s/vue-chart-issue-v2-twg3o
I've spent nearly a week trying to figure this out with no joy. I could create a workaround to use a separate ChartRender component for each chart type (e.g. ChartRenderBar, ChartRenderLine etc) but it moves away from DRY, so would rather not.
If anybody could help, I'd be VERY appreciative,
It is possible to dynamically update your chart type with vue-chartjs. The way I did it is by accessing the options in the chart itself and replacing it with the prop I get in which says which chart type it should become and then do an update on the chart. It is not the most elegant solution but it works.
<script>
import { Line, mixins } from 'vue-chartjs';
const { reactiveProp } = mixins;
export default {
extends: Line,
name: "LineChart",
mixins: [reactiveProp],
props: {
options: { type: Object },
chartType: { type: String }
},
mounted () {
this.renderChart(this.chartData, this.options);
},
watch: {
options: {
deep: true,
handler () {
this.$data._chart.options = this.options;
this.updateChart();
}
},
chartType (newVal) {
this.$data._chart.config.type = newVal;
this.updateChart()
}
},
methods: {
updateChart () {
this.$data._chart.update();
},
}
}
</script>
in Vuejs, it is not possible to change mixins after the component being created, and because of this I've used a wrapper component in my other solution, so I can pass a mixin dynamically before the component being created, but unfortunately, there is no way to have some kind of reactive mixin.
my solution for you current situation would be something like that:
https://codesandbox.io/s/vue-template-y5wsw
in the above solution, I have created two components, BarChart and LineChart
to switch between those dynamically, I am using one of the most awesome features in vuejs, Dynamic Component
and of course to avoid duplicating the data source, you can use vuex to share data between multiple components, or you can have the data in the parent page and access your dataset or options like
this.$parent['whatever data property in your parent component']
Hope you found this helpful.
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
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.