I am quite new with VueJS and I have been having trouble lately with some computed properties which do not update as I would like. I've done quite some research on Stack Overflow, Vue documentation and other ressources but i haven't found any solution yet.
The "app" is basic. I've got a parent component (Laundry) which has 3 child components (LaundryMachine). The idea is to have for each machine a button which displays its availability and updates the latter when clicked on.
In order to store the availability of all machines, I have a data in the parent component (availabilities) which is an array of booleans. Each element corresponds to a machine's availability.
When I click on the button, I know the array availibities updates correctly thanks to the console.log. However, for each machine, the computed property "available" does not update is I would want it to and I have no clue why.
Here is the code
Parent component:
<div id="machines">
<laundry-machine
name="AA"
v-bind:machineNum="0"
v-bind:availableArray="this.availabilities"
v-on:change-avlb="editAvailabilities"
></laundry-machine>
<laundry-machine
name="BB"
v-bind:machineNum="1"
v-bind:availableArray="this.availabilities"
v-on:change-avlb="editAvailabilities"
></laundry-machine>
<laundry-machine
name="CC"
v-bind:machineNum="2"
v-bind:availableArray="this.availabilities"
v-on:change-avlb="editAvailabilities"
></laundry-machine>
</div>
</div>
</template>
<script>
import LaundryMachine from './LaundryMachine.vue';
export default {
name: 'Laundry',
components: {
'laundry-machine': LaundryMachine
},
data: function() {
return {
availabilities: [true, true, true]
};
},
methods: {
editAvailabilities(index) {
this.availabilities[index] = !this.availabilities[index];
console.log(this.availabilities);
}
}
};
</script>
Child component:
<template>
<div class="about">
<h2>{{ name }}</h2>
<img src="../assets/washing_machine.png" /><br />
<v-btn color="primary" v-on:click="changeAvailability">
{{ this.availability }}</v-btn>
</div>
</template>
<script>
export default {
name: 'LaundryMachine',
props: {
name: String,
machineNum: Number,
availableArray: Array
},
methods: {
changeAvailability: function(event) {
this.$emit('change-avlb', this.machineNum);
console.log(this.availableArray);
console.log('available' + this.available);
}
},
computed: {
available: function() {
return this.availableArray[this.machineNum];
},
availability: function() {
if (this.available) {
return 'disponible';
} else {
return 'indisponible';
}
}
}
};
</script>
Anyway, thanks in advance !
Your problem comes not from the computed properties in the children, rather from the editAvailabilities method in the parent.
The problem is this line in particular:
this.availabilities[index] = !this.availabilities[index];
As you can read here, Vue has problems tracking changes when you modify an array by index.
Instead, you should do:
this.$set(this.availabilities, index, !this.availabilities[index]);
To switch the value at that index and let Vue track that change.
Related
I am building an MVP and this is the first time I do web development. I am using Vue2 and Firebase and so far, things go well.
However, I ran into a problem I cannot solve alone. I have an idea how it SHOULD work but cannot write it into code and hope you guys can help untangle my mind. By now I am incredibly confused and increasingly frustrated :D
So lets see what I got:
Child Component
I have built a child component which is a form with three text-areas. To keep it simple, only one is included it my code snippets.
<template>
<div class="wrap">
<form class="form">
<p class="label">Headline</p>
<textarea rows="2"
v-model="propHeadline"
:readonly="readonly">
</textarea>
// To switch between read and edit
<button
v-if="readonly"
#click.prevent="togglemode()">
edit
</button>
<button
v-else
type="submit"
#click.prevent="togglemode(), updatePost()"
>
save
</button>
</form>
</div>
</template>
<script>
export default {
name: 'PostComponent'
data() {
return {
readonly: true
}
},
props: {
propHeadline: {
type: String,
required: true
}
},
methods: {
togglemode() {
if (this.readonly) {
this.readonly = false
} else {
this.readonly = true
}
},
updatePost() {
// updates it to the API - that works
}
}
}
</script>
<script src="https://cdnjs.cloudflare.com/ajax/libs/vue/2.5.17/vue.js"></script>
And my parent component:
<template>
<div class="wrap">
<PostComponent
v-for="post in posts"
:key="post.id"
:knugHeadline="post.headline"
/>
</div>
</template>
<script>
import PostComponent from '#/components/PostComponent.vue'
export default {
components: { PostComponent },
data() {
return {
posts: []
}
},
created() {
// Gets all posts from DB and pushes them in array "posts"
}
</script>
<script src="https://cdnjs.cloudflare.com/ajax/libs/vue/2.5.17/vue.js"></script>
Current Status
So far, everything works. I can display all posts and when clicking on "edit" I can make changes and save them. Everything gets updated to Firebase - great!
Problem / Error Message
I get the following error message:
[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.
As the error says I should use a computed property based on the props value. But how can I achieve that?
Solution Approach
I believe I have to use a computed getter to return the prop value - how to do that?
And then I have to use the setter to emit an event to the parent to update the value so the prop passes it back down - how to do that?
I have found bits and pieces online but by now all I see is happy families passing around small packages of data...
Would be really thankful for a suggestion on how to solve this one! :)
Thanks a lot!
This error shows because of your v-model on texterea which mutate the prop, but in vue it is illegal to mutate props :
<textarea rows="2"
v-model="propHeadline"
:readonly="readonly">
</textarea>
So, what you could do is to use this created() lifecycle hook and set the propHeadline prop as data :
<script>
export default {
name: 'PostComponent'
data() {
return {
readonly: true,
headline: ""
}
},
props: {
propHeadline: {
type: String,
required: true
}
},
created() {
this.headline = this.propHeadline
}
}
</script>
An then, update the new variable on your textarea :
<textarea rows="2"
v-model="headline"
:readonly="readonly">
</textarea>
I'm new to Vue and was hoping for some clarification on best practices.
I'm building an app that uses an array to keep a list of child components and I want to be able to update and remove components by emiting to the parent. To accomplish this I currently have the child check the parent array to find it's index with an "equals" method so that it can pass that index to the parent. This works fine for something simple but if my child components get more complex, there will be more and more data points I'll have to check to make sure I'm changing the correct one. Another way to do this that I can think of is to give the child component an ID prop when it's made and just pass that but then I'd have to handle making sure all the ids are different.
Am I on the right track or is there a better more widely accepted way to do this? I've also tried using indexOf(this._props) to get the index but that doesn't seem to work. Maybe I'm just doing something wrong?
Here's a simplified version of what I'm doing:
// fake localStorage for snippet sandbox
const localStorage = {}
Vue.component('child', {
template: '#template',
data() {
return {
newName: this.name
}
},
props: {
name: String
},
mounted() {
this.newName = this.name
},
methods: {
update() {
this.$emit(
"update-child",
this.$parent.children.findIndex(this.equals),
this.newName
)
},
equals(a) {
return a.name == this.name
}
}
})
var app = new Vue({
el: '#app',
data: {
children: []
},
methods: {
addNewChild() {
this.children.push({
name: 'New Child',
})
},
updateChild(index, newName) {
this.children[index].name = newName
}
},
mounted() {
if (localStorage.children) {
this.children = JSON.parse(localStorage.children)
}
},
watch: {
children(newChildren) {
localStorage.children = JSON.stringify(newChildren)
}
}
})
<script src="https://cdn.jsdelivr.net/npm/vue/dist/vue.min.js"></script>
<div id="app">
<button v-on:click="addNewChild">+ New Child</button>
<hr />
<child v-for="child in children"
:key="children.indexOf(child)"
:name="child.name"
#update-child="updateChild">
</child>
</div>
<script type="text/x-template" id="template">
<div>
<p><b>Name: {{name}}</b></p>
<input placeholder="Name" type="text" v-model="newName" />
<button #click="update">Update</button>
<hr />
</div>
</script>
The great thing about v-for is that it creates its own scope. With that in mind, you can safely reference child in the event handler. For example
<child
v-for="(child, index) in children"
:key="index"
:name="child.name"
#update-child="updateChild(child, $event)"
/>
updateChild(child, newName) {
child.name = newName
}
All you need to emit from your child component is the new name which will be presented as the event payload $event
update() {
this.$emit("update-child", this.newName)
}
A quick note about :key... it would definitely be better to key on some unique property of the child object (like an id as you suggested).
Keying on array indices is fine if your array only changes in size but if you ever decide to splice or sort it, Vue won't be able to react to that change correctly since the indices never change.
I have a question why not this component, not re-rendering after changing value so what I'm trying to do is a dynamic filter like amazon using the only checkboxes so let's see
I have 4 components [ App.vue, test-filter.vue, filtersInputs.vue, checkboxs.vue]
Here is code sandbox for my example please check the console you will see the value changing https://codesandbox.io/s/thirsty-varahamihira-nhgex?file=/src/test-filter/index.vue
the first component is App.vue;
<template>
<div id="app">
<h1>Filter</h1>
{{ test }}
<test-filter :filters="filters" :value="test"></test-filter>
</div>
</template>
<script>
import testFilter from "./test-filter";
import filters from "./filters";
export default {
name: "App",
components: {
testFilter,
},
data() {
return {
filters: filters,
test: {},
};
},
};
</script>
so App.vue that holds the filter component and the test value that I want to display and the filters data is dummy data that hold array of objects.
in my test-filter component, I loop throw the filters props and the filterInputs component output the input I want in this case the checkboxes.
test-filter.vue
<template>
<div class="test-filter">
<div
class="test-filter__filter-holder"
v-for="filter in filters"
:key="filter.id"
>
<p class="test-filter__title">
{{ filter.title }}
</p>
<filter-inputs
:value="value"
:filterType="filter.filter_type"
:options="filter.options"
#checkboxChanged="checkboxChanged"
></filter-inputs>
</div>
</div>
<template>
<script>
import filterInputs from "./filterInputs";
export default {
name: "test-filter",
components: {
filterInputs,
},
props:{
filters: {
type: Array,
default: () => [],
},
value: {
type: Array,
default: () => ({}),
},
},
methods:{
checkboxChanged(value){
// Check if there is a array in checkbox key if not asssign an new array.
if (!this.value.checkbox) {
this.value.checkbox = [];
}
this.value.checkbox.push(value)
}
};
</script>
so I need to understand why changing the props value also change to the parent component and in this case the App.vue and I tried to emit the value to the App.vue also the component didn't re-render but if I check the vue dev tool I see the value changed but not in the DOM in {{ test }}.
so I will not be boring you with more code the filterInputs.vue holds child component called checkboxes and from that, I emit the value of selected checkbox from the checkboxes.vue to the filterInputs.vue to the test-filter.vue and every component has the value as props and that it if you want to take a look the rest of components I will be glad if you Did.
filterInpust.vue
<template>
<div>
<check-box
v-if="filterType == checkboxName"
:options="options"
:value="value"
#checkboxChanged="checkboxChanged"
></check-box>
</div>
</template>
<script>
export default {
props: {
value: {
type: Object,
default: () => ({}),
},
options: {
type: Array,
default: () => [],
},
methods: {
checkboxChanged(value) {
this.$emit("checkboxChanged", value);
},
},
}
</script>
checkboxes.vue
<template>
<div>
<div
v-for="checkbox in options"
:key="checkbox.id"
>
<input
type="checkbox"
:id="`id_${_uid}${checkbox.id}`"
#change="checkboxChange"
:value="checkbox"
/>
<label
:for="`id_${_uid}${checkbox.id}`"
>
{{ checkbox.title }}
</label>
</div>
</div>
<template>
<script>
export default {
props: {
value: {
type: Object,
default: () => ({}),
},
options: {
type: Array,
default: () => [],
},
}
methods: {
checkboxChange(event) {
this.$emit("checkboxChanged", event.target.value);
},
},
};
</script>
I found the solution As I said in the comments the problem was that I'm not using v-model in my checkbox input Vue is a really great framework the problem wasn't in the depth, I test the v-model in my checkbox input and I found it re-render the component after I select any checkbox so I search more and found this article and inside of it explained how we can implement v-model in the custom component so that was the solution to my problem and also I update my codeSandbox Example if you want to check it out.
Big Thaks to all who supported me to found the solution: sarkiroka, Jakub A Suplick
I have made a global component that will render the content we want.
This component is very simple
<template>
<section
id="help"
class="collapse"
>
<div class="container-fluid">
<slot />
</div>
</section>
</template>
<script>
export default {
name: 'VHelp',
};
</script>
I use it inside my base template with
<v-help />
I'm trying to add content to this component slot from another single file component using.
<v-help>
<p>esgssthsrthsrt</p>
</v-help>
But this logically create another instance of my comp, with the p tag inside. Not the correct thing I want to do.
So I tried with virtual DOM and rendering function, replacing slot by <v-elements-generator :elements="$store.state.help.helpElements" /> inside my VHelp comp.
The store helpElements is a simple array with objects inside.
{
type: 'a',
config: {
class: 'btn btn-default',
},
nestedElements: [
{
type: 'span',
value: 'example',
},
{
type: 'i',
},
],
},
Then inside my VElementsGenerator comp I have a render function that with render element inside virtual DOM from an object like
<script>
import {
cloneDeep,
isEmpty,
} from 'lodash';
export default {
name: 'VElementsGenerator',
props: {
elements: {
type: Array,
required: true,
},
},
methods: {
iterateThroughObject(object, createElement, isNestedElement = false) {
const generatedElement = [];
for (const entry of object) {
const nestedElements = [];
let elementConfig = {};
if (typeof entry.config !== 'undefined') {
elementConfig = cloneDeep(entry.config);
}
if (entry.nestedElements) {
nestedElements.push(this.iterateThroughObject(entry.nestedElements, createElement, true));
}
generatedElement.push(createElement(
entry.type,
isEmpty(elementConfig) ? entry.value : elementConfig,
nestedElements
));
if (typeof entry.parentValue !== 'undefined') {
generatedElement.push(entry.parentValue);
}
}
if (isNestedElement) {
return generatedElement.length === 1 ? generatedElement[0] : generatedElement;
}
return createElement('div', generatedElement);
},
},
render(createElement) {
if (this.elements) {
return this.iterateThroughObject(this.elements, createElement);
}
return false;
},
};
</script>
This second method is working well but if I want to render complex data, the object used inside the rendering function is very very long and complex to read.
So I'm trying to find another way to add content to a global component used inside a base layout only when I want it on a child component.
I can't use this VHelp component directly inside children comps because the HTML page architecture will be totally wrong.
I'm wondering if this is possible to add content (preferably HTML) to a component slot from a single file comp without re-creating a new instance of the component?
Furthermore I think this is very ugly to save HTML as string inside a Vuex store. So I don't even know if this is possible and if I need to completely change the way I'm trying to do this.
Any ideas ?
In the store, you should only store data and not an HTML structure. The way to go with this problem would be to store the current state of the content of the v-help component in the store. Then, you would have a single v-help component with a slot (like you already proposed). You should pass different contents according to the state in the store. Here is an abstract example:
<v-help>
<content-one v-if="$store.state.content === 'CONTENT_ONE' />
<content-two v-else-if="$store.state.content === 'CONTENT_TWO' />
<content-fallback v-else />
</v-help>
Child element somewhere else:
<div>
<button #click="$store.commit('setContentToOne')">Content 1</button>
</div>
Vuex Store:
state: {
content: null
},
mutations: {
setContentToOne(state) {
state.content = 'CONTENT_ONE';
}
}
Of course it depends on your requirements and especially on how many different scenarios are used if this is the best way to achieve this. If I understood you correctly, you are saving help elements to the store. You could also save an array of currently selected help elements in there and just display them directly in the v-help component.
EDIT:
Of course you can also just save the static component (or its name) in the store. Then, you could dynamically decide in the child components, which content is shown in v-help. Here is an example:
<v-help>
<component :is="$store.state.helpComponent" v-if="$store.state.helpComponent !== null" />
</v-help>
Test Component:
<template>
test component
</template>
<script>
export default {
name: 'test-component'
};
</script>
Child element somewhere else (variant 1, storing the name in Vuex):
<div>
<button #click="$store.commit('setHelpComponent', 'test-component')">Set v-help component to 'test-component'</button>
</div>
Child element somewhere else (variant 2, storing the whole component in Vuex):
<template>
<button #click="$store.commit('setHelpComponent', testComponent)">Set v-help component to testComponent (imported)</button>
</template>
<script>
import TestComponent from '#/components/TestComponent';
export default {
name: 'some-child-component',
computed: {
testComponent() {
return TestComponent;
}
}
};
</script>
Child element somewhere else (variant 3, storing the name, derived from the imported component, in Vuex; I would go with this variant):
<template>
<button #click="$store.commit('setHelpComponent', testComponentName)">Set v-help component to 'test-component'</button>
</template>
<script>
import TestComponent from '#/components/TestComponent';
export default {
name: 'some-child-component',
computed: {
testComponentName() {
return TestComponent.name;
}
}
};
</script>
Vuex Store:
state: {
helpComponent: null
},
mutations: {
setHelpComponent(state, value) {
state.helpComponent = value;
}
}
See also the documentation for dynamic components (<component :is=""> syntax): https://v2.vuejs.org/v2/guide/components.html#Dynamic-Components
Problem
Let's say I have a vue component called:
Note: All vue components has been simplified to explain what I'm trying to do.
reusable-comp.vue
<template>
<div class="input-group input-group-sm">
<input type="text" :value.number="setValue" class="form-control" #input="$emit('update:setValue', $event.target.value)">
<span>
<button #click="incrementCounter()" :disabled="disabled" type="button" class="btn btn-outline-bordercolor btn-number" data-type="plus">
<i class="fa fa-plus gray7"></i>
</button>
</span>
</div>
</template>
<script>
import 'font-awesome/css/font-awesome.css';
export default {
props: {
setValue: {
type: Number,
required: false,
default: 0
}
},
data() {
return {
}
},
methods: {
incrementCounter: function () {
this.setValue += 1;
}
}
}
</script>
Then in a parent component I do something like this:
subform.vue
<div class="row mb-1">
<div class="col-md-6">
Increment Value of Num A
</div>
<div class="col-md-6">
<reuseable-comp :setValue.sync="numA"></reuseable-comp>
</div>
</div>
<script>
import reusableComp from '../reusable-comp'
export default {
components: {
reusableComp
},
props: {
numA: {
type: Number,
required: false,
default: 0
}
},
data() {
return {
}
}
</script>
then lastly
page_layout.vue
<template>
<div>
<subform :numA.sync="data1" />
</div>
</template>
<script>
import subform from '../subform.vue'
export default {
components: {
subform
},
data() {
return {
data1: 0
}
}
}
</script>
Question
So, how do I sync a value between reusable-comp.vue, subform.vue, and page_layout.vue
I'm using reuseable-comp.vue is many different places. I'm using subform.vue only a couple times in page_layout.vue
And I'm trying to use this pattern several times. But I can't seem to get this to work. The above gives me an error:
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: "numA"
Okay I found a solution that worked.
In subform.vue, we change:
data() {
return {
numA_data : this.numA
}
}
So we now have reactive data to work with. Then in the template, we refer to that reactive data instead of the prop:
<reuseable-comp :setValue.sync="numA_data"></reuseable-comp>
Then finally we add a watcher to check if the reactive data gets changed, and then emit to the parent:
watch: {
numA_data: function(val) {
this.$emit('update:numA', this.numA_data);
}
}
Now all values from grandchildren to parent are synced.
Update (4/13/2018)
I made new changes to the reusable-comp.vue:
I replaced where it says 'setValue' to 'value'
I replaced where it says 'update:value' to 'input'
Everything else says the same.
Then in subform.vue:
I replaced ':setValue.sync' to 'v-model'
v-model is two way binding, so I made use of that where it needed to be. The sync between the parent-child (not child to grandchild), is still using sync modifier, only because the parent has many props to pass. I could modify this where I could group up the props as a single object, and just pass that.