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Dynamics inputs, the v-model update all values in v-for

I try this following code with Vue.js 2:
<div id="app">
<div v-for="(item, index) in items">
<div>
<input type="text" v-model="items[index].message">
<input type="text" v-model="items[index].surface">
</div>
</div>
<button #click="addNewfield">Add</button>
</div>
var app = new Vue({
el: '#app',
data: {
item: {
message: 'test',
surface: 45
},
items: [],
},
mounted() {
this.items.push(this.item)
},
methods: {
addNewfield() {
this.items.push(this.item);
}
}
})
The goal is to create news input when user click on Add button. I tried different ways like :
<input type="text" v-model="item.message">
But it doesn't work. If you write in "message" input, all "message" inputs will be updated.
How can I only updated the concerned value ?
Thanks for help !

This is happening because objects in Javascript are stored by reference. This means that every time you push this.item onto the array, it's adding a reference to the exact same object as the last.
You can avoid this by creating a new object each time:
methods: {
addNewfield() {
const obj = {
message: 'test',
surface: 45
}
this.items.push(obj);
}
}
Another option would be to clone the original object each time like:
methods: {
addNewfield() {
const clone = Object.assign({}, this.item);
this.items.push(clone);
}
}

Vue.js - Computed property not updating - child component

I've created a simple component named DefaultButton.
It bases on properties, that are being set up whenever this component is being created.
The point is that after mounting it, It does not react on changes connected with "defaultbutton", that is an object located in properties
<template>
<button :class="buttonClass" v-if="isActive" #click="$emit('buttonAction', defaultbutton.id)" >
{{ this.defaultbutton.text }}
</button>
<button :class="buttonClass" v-else disabled="disabled">
{{ this.defaultbutton.text }}
</button>
</template>
<script>
export default {
name: "defaultbutton",
props: {
defaultbutton: Object
},
computed: {
buttonClass() {
return `b41ngt ${this.defaultbutton.state}`;
},
isActive() {
return (this.defaultbutton.state === "BUTTON_ACTIVE" || this.defaultbutton.state === "BUTTON_ACTIVE_NOT_CHOSEN");
}
}
};
</script>
Having following component as a parent one:
<template>
<div v-if="state_items.length == 2" class="ui placeholder segment">
{{ this.state_items[0].state }}
{{ this.state_items[1].state }}
{{ this.current_active_state }}
<div class="ui two column very relaxed stackable grid">
<div class="column">
<default-button :defaultbutton="state_items[0]" #buttonAction="changecurrentstate(0)"/>
</div>
<div class="middle aligned column">
<default-button :defaultbutton="state_items[1]" #buttonAction="changecurrentstate(1)"/>
</div>
</div>
<div class="ui vertical divider">
Or
</div>
</div>
</template>
<script type="text/javascript">
import DefaultButton from '../Button/DefaultButton'
export default {
name: 'changestatebox',
data() {
return {
current_active_state: 1
}
},
props: {
state_items: []
},
components: {
DefaultButton
},
methods: {
changecurrentstate: function(index) {
if(this.current_active_state != index) {
this.state_items[this.current_active_state].state = 'BUTTON_ACTIVE_NOT_CHOSEN';
this.state_items[index].state = 'BUTTON_ACTIVE';
this.current_active_state = index;
}
},
},
mounted: function () {
this.state_items[0].state = 'BUTTON_ACTIVE';
this.state_items[1].state = 'BUTTON_ACTIVE_NOT_CHOSEN';
}
}
</script>
It clearly shows, using:
{{ this.state_items[0].state }}
{{ this.state_items[1].state }}
{{ this.current_active_state }}
that the state of these items are being changed, but I am unable to see any results on the generated "DefaultButtons". Classes of objects included in these components are not being changed.
#edit
I've completely changed the way of delivering the data.
Due to this change, I've abandoned the usage of an array; instead I've used two completely not related object.
The result is the same - class of the child component's object is not being
DefaulButton.vue:
<template>
<button :class="buttonClass" v-if="isActive" #click="$emit('buttonAction', defaultbutton.id)" >
{{ this.defaultbutton.text }}
</button>
<button :class="buttonClass" v-else disabled="disabled">
{{ this.defaultbutton.text }}
</button>
</template>
<style lang="scss">
import './DefaultButton.css';
</style>
<script>
export default {
name: "defaultbutton",
props: {
defaultbutton: {
type: Object,
default: () => ({
id: '',
text: '',
state: '',
})
}
},
computed: {
buttonClass() {
return `b41ngt ${this.defaultbutton.state}`;
},
isActive() {
return (this.defaultbutton.state === "BUTTON_ACTIVE" ||
this.defaultbutton.state === "BUTTON_ACTIVE_NOT_CHOSEN");
}
}
};
</script>
ChangeStateBox.vue:
<template>
<div class="ui placeholder segment">
{{ this.state_first.state }}
{{ this.state_second.state }}
{{ this.current_active_state }}
<div class="ui two column very relaxed stackable grid">
<div class="column">
<default-button :defaultbutton="state_first" #buttonAction="changecurrentstate(0)"/>
</div>
<div class="middle aligned column">
<default-button :defaultbutton="state_second" #buttonAction="changecurrentstate(1)"/>
</div>
</div>
<div class="ui vertical divider">
Or
</div>
</div>
</template>
<script type="text/javascript">
import DefaultButton from '../Button/DefaultButton'
export default {
name: 'changestatebox',
data() {
return {
current_active_state: 1
}
},
props: {
state_first: {
type: Object,
default: () => ({
id: '',
text: ''
})
},
state_second: {
type: Object,
default: () => ({
id: '',
text: ''
})
},
},
components: {
DefaultButton
},
methods: {
changecurrentstate: function(index) {
if(this.current_active_state != index) {
if(this.current_active_state == 1){
this.$set(this.state_first, 'state', "BUTTON_ACTIVE_NOT_CHOSEN");
this.$set(this.state_second, 'state', "BUTTON_ACTIVE");
} else {
this.$set(this.state_first, 'state', "BUTTON_ACTIVE");
this.$set(this.state_second, 'state', "BUTTON_ACTIVE_NOT_CHOSEN");
}
this.current_active_state = index;
}
},
},
created: function () {
this.state_first.state = 'BUTTON_ACTIVE';
this.state_second.state = 'BUTTON_ACTIVE_NOT_CHOSEN';
}
}
</script>

You're declaring props wrong. It is either an array of prop names or it is an object with one entry for each prop declaring its type, or it is an object with one entry for each prop declaring multiple properties.
You have
props: {
state_items: []
},
but to supply a default it should be
props: {
state_items: {
type: Array,
default: []
}
},
But your problem is most likely that you're mutating state_items in such a way that Vue can't react to the change

Your main problem is the way you are changing the button state, according with Array change detection vue can't detect mutations by indexing.
Due to limitations in JavaScript, Vue cannot detect the following
changes to an array:
When you directly set an item with the index, e.g.
vm.items[indexOfItem] = newValue When you modify the length of the
array, e.g. vm.items.length = newLength

In case someone will be having the same issue:
#Roy J as well as #DobleL were right.
The reason behind this issue was related with the wrong initialization of state objects.
According to the documentation:
Vue cannot detect property addition or deletion.
Since Vue performs the getter/setter conversion process during instance
initialization, a property must be present in the
data object in order for Vue to convert it and make it reactive.
Before reading this sentence, I used to start with following objects as an initial data:
var local_state_first = {
id: '1',
text: 'Realized',
};
var local_state_second = {
id: '2',
text: 'Active'
};
and the correct version of it looks like this:
var local_state_first = {
id: '1',
text: 'Realized',
state: 'BUTTON_ACTIVE'
};
var local_state_second = {
id: '2',
text: 'Active',
state: 'BUTTON_ACTIVE'
};
whereas declaring the main component as:
<change-state-box :state_first="local_state_first" :state_second="local_state_second" #buttonAction="onbuttonAction"/>
Rest of the code remains the same ( take a look at #edit mark in my main post )

Input field unable to change model when component and model are dynamically created

I have a data structure with nested objects that I want to bind to sub-components, and I'd like these components to edit the data structure directly so that I can save it all from one place. The structure is something like
job = {
id: 1,
uuid: 'a-unique-value',
content_blocks: [
{
id: 5,
uuid: 'some-unique-value',
block_type: 'text',
body: { en: { content: 'Hello' }, fr: { content: 'Bonjour' } }
},
{
id: 9,
uuid: 'some-other-unique-value',
block_type: 'text',
body: { en: { content: 'How are you?' }, fr: { content: 'Comment ça va?' } }
},
]
}
So, I instantiate my sub-components like this
<div v-for="block in job.content_blocks" :key="block.uuid">
<component :data="block" :is="contentTypeToComponentName(block.block_type)" />
</div>
(contentTypeToComponentName goes from text to TextContentBlock, which is the name of the component)
The TextContentBlock goes like this
export default {
props: {
data: {
type: Object,
required: true
}
},
created: function() {
if (!this.data.body) {
this.data.body = {
it: { content: "" },
en: { content: "" }
}
}
}
}
The created() function takes care of adding missing, block-specific data that are unknown to the component adding new content_blocks, for when I want to dynamically add blocks via a special button, which goes like this
addBlock: function(block_type) {
this.job.content_blocks = [...this.job.content_blocks, {
block_type: block_type,
uuid: magic_uuidv4_generator(),
order: this.job.content_blocks.length === 0 ? 1 : _.last(this.job.content_blocks).order + 1
}]
}
The template for TextContentBlock is
<b-tab v-for="l in ['fr', 'en']" :key="`${data.uuid}-${l}`">
<template slot="title">
{{ l.toUpperCase() }} <span class="missing" v-show="!data.body[l] || data.body[l] == ''">(missing)</span>
</template>
<b-form-textarea v-model="data.body[l].content" rows="6" />
<div class="small mt-3">
<code>{{ { block_type: data.block_type, uuid: data.uuid, order: data.order } }}</code>
</div>
</b-tab>
Now, when I load data from the API, I can correctly edit and save the content of these blocks -- which is weird considering that props are supposed to be immutable.
However, when I add new blocks, the textarea above wouldn't let me edit anything. I type stuff into it, and it just deletes it (or, I think, it replaces it with the "previous", or "initial" value). This does not happen when pulling content from the API (say, on page load).
Anyway, this led me to the discovery of immutability, I then created a local copy of the data prop like this
data: function() {
return {
block_data: this.data
}
}
and adjusted every data to be block_data but I get the same behaviour as before.
What exactly am I missing?

As the OP's comments, the root cause should be how to sync textarea value between child and parent component.
The issue the OP met should be caused by parent component always pass same value to the textarea inside the child component, that causes even type in something in the textarea, it still bind the same value which passed from parent component)
As Vue Guide said:
v-model is essentially syntax sugar for updating data on user input
events, plus special care for some edge cases.
The syntax sugar will be like:
the directive=v-model will bind value, then listen input event to make change like v-bind:value="val" v-on:input="val = $event.target.value"
So adjust your codes to like below demo:
for input, textarea HTMLElement, uses v-bind instead of v-model
then uses $emit to popup input event to parent component
In parent component, uses v-model to sync the latest value.
Vue.config.productionTip = false
Vue.component('child', {
template: `<div class="child">
<label>{{value.name}}</label><button #click="changeLabel()">Label +1</button>
<textarea :value="value.body" #input="changeInput($event)"></textarea>
</div>`,
props: ['value'],
methods: {
changeInput: function (ev) {
let newData = Object.assign({}, this.value)
newData.body = ev.target.value
this.$emit('input', newData) //emit whole prop=value object, you can only emit value.body or else based on your design.
// you can comment out `newData.body = ev.target.value`, then you will see the result will be same as the issue you met.
},
changeLabel: function () {
let newData = Object.assign({}, this.value)
newData.name += ' 1'
this.$emit('input', newData)
}
}
});
var vm = new Vue({
el: '#app',
data: () => ({
options: [
{id: 0, name: 'Apple', body: 'Puss in Boots'},
{id: 1, name: 'Banana', body: ''}
]
}),
})
.child {
border: 1px solid green;
}
<script src="https://unpkg.com/vue#2.5.16/dist/vue.js"></script>
<div id="app">
<span> Current: {{options}}</span>
<hr>
<div v-for="(item, index) in options" :key="index">
<child v-model="options[index]"></child>
</div>
</div>

Getting index of a data in an array in VUE js

I want to change the status of Tasks when a particular method is called. But The problem is I cannot get the index of the particular item of the array to change its status.
This is my HTML:
<div class="main" id="my-vue-app">
<ul>
<li v-for="task in completeTask">
{{ task.description }} <button #click="markIncomplete">Mark as Incomplete</button>
</li>
</ul>
<ul>
<li v-for="task in incompleteTask">
{{ task.description }} <button #click="markComplete">Mark as Complete</button>
</li>
</ul>
</div>
And this is my Vue:
<script>
new Vue(
{
el: '#my-vue-app',
data:
{
tasks: [
{description:'go to market', status: true},
{description:'buy book', status: true},
{description:'eat biriani', status: true},
{description:'walk half kilo', status: false},
{description:'eat icecream', status: false},
{description:'return to home', status: false}
]
},
computed:
{
incompleteTask()
{
return this.tasks.filter(task => ! task.status);
},
completeTask()
{
return this.tasks.filter(task => task.status);
}
},
methods:
{
markComplete()
{
return this.task.status = true;
},
markIncomplete()
{
return this.task.status = false;
}
}
}
)
</script>
I need make use of markComplete() and markIncomplete() but the problem is I couldn't find the way to get the index of current element to change its status.

You could get the index by declaring a second argument at the v-for:
<li v-for="(task, index) in incompleteTask">
{{ task.description }} <button #click="markComplete(index)">Mark as Complete</button>
</li>
methods:
{
markComplete(index)
{
return this.tasks[index].status = true;
},
But a, maybe simpler, alternative is to simply **pass the `task` as argument**:
<li v-for="task in incompleteTask">
{{ task.description }} <button #click="markComplete(task)">Mark as Complete</button>
</li>
methods:
{
markComplete(task)
{
return task.status = true;
},

RTFM:
You can use the v-repeat directive to repeat a template element
based on an Array of objects on the ViewModel. For every object in the
Array, the directive will create a child Vue instance using that
object as its $data object. These child instances inherit all data
on the parent, so in the repeated element you have access to
properties on both the repeated instance and the parent instance. In
addition, you get access to the $index property, which will be the
corresponding Array index of the rendered instance.
var demo = new Vue({
el: '#demo',
data: {
parentMsg: 'Hello',
items: [
{ childMsg: 'Foo' },
{ childMsg: 'Bar' }
]
}
})
<script src="https://unpkg.com/vue#0.12.16/dist/vue.min.js"></script>
<ul id="demo">
<li v-repeat="items" class="item-{{$index}}">
{{$index}} - {{parentMsg}} {{childMsg}}
</li>
</ul>
Source:
https://012.vuejs.org/guide/list.html
Note: The directive v-repeat is available in old versions of Vue.js :-)

How to refresh Vue components upon list item removal?

I know how to remove a list item from a Vue instance. However, when list items are passed to Vue components, how to remove a list item while keeping the components in sync with the list data?
Here is the use case. Consider an online forum with a Markdown editor. We have a Vue instance whose data are a list of saved comments fetched from a server. These comments are supposed to be written in Markdowns.
To facilitate edits and previews, we also have a list of components. Each component contains an editable input buffer as well as a preview section. The content of the saved comment in the Vue instance is used to initialise the input buffer and to reset it when a user cancels an edit. The preview is a transformation of the content of the input buffer.
Below is a test implementation:
<template id="comment">
<div>
Component:
<textarea v-model="input_buffer" v-if="editing"></textarea>
{{ preview }}
<button type="button" v-on:click="edit" v-if="!editing">edit</button>
<button type="button" v-on:click="remove" v-if="!editing">remove</button>
<button type="button" v-on:click="cancel" v-if="editing">cancel</button>
</div>
</template>
<div id="app">
<ol>
<li v-for="(comment, index) in comments">
<div>Instance: {{comment}}</div>
<comment
v-bind:comment="comment"
v-bind:index="index"
v-on:remove="remove">
</comment>
</li>
</ol>
</div>
<script src="https://cdnjs.cloudflare.com/ajax/libs/vue/2.1.8/vue.js"></script>
<script>
let comments = ['111', '222', '333']
Vue.component('comment', {
template: '#comment',
props: ['comment', 'index'],
data: function() {
return {
input_buffer: '',
editing: false,
}
},
mounted: function() { this.cancel() },
computed: {
preview: function() {
// This is supposed to be a transformation of the input buffer,
// but for now, let's simply output the input buffer
return this.input_buffer
},
},
methods: {
edit: function() { this.editing = true },
remove: function() { this.$emit('remove', this.index) },
cancel: function() { this.input_buffer = this.comment; this.editing = false },
//save: function() {}, // submit to server; not implemented yet
},
})
let app = new Vue({
el: '#app',
data: { comments: comments },
methods: {
remove: function(index) { this.comments.splice(index, 1); app.$forceUpdate() },
},
})
</script>
The problem is that, if we remove a comment, the components are not refreshed accordingly. For example, we have 3 comments in the above implementation. if you remove comment 2, the preview of item 3 will still show the content of item 2. It is updated only if we press edit followed by cancel.
I've tried app.$forceUpdate(), but that didn't help.

You just need to add key attribute in the v-for loop like following:
<li v-for="(comment, index) in comments" :key="comment">
See working fiddle: https://fiddle.jshell.net/mimani/zLrLvqke/
Vue tries to optimises rendering, by providing key attribute, it treats those as completely different elements and re-renders those properly.
See the key documentation for more information.

try with:
Vue.component('comment', {
template:
`<div>
{{ comment }}
<button v-on:click="remove"> X </button>
</div>`,
props: ['comment', 'index'],
methods: {
remove: function() {
this.$emit('remove', this.index);
}
},
});
vm = new Vue({
el: '#app',
data: {
comments: ['a','b','c','d','e']
},
methods: {
remove: function(index) {
this.comments.splice(index, 1);
},
},
});
<script src="https://cdnjs.cloudflare.com/ajax/libs/vue/2.1.8/vue.min.js"></script>
<div id="app">
<ol>
<li v-for="(comment, index) in comments">
<comment
v-bind:comment="comment"
v-bind:index="index"
v-on:remove="remove">
</comment>
</li>
</ol>
</div>