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

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);
}
}

Related

Updating a data property in Vuejs based on an input event

I have a search input that filters data. The filtered data is meant to re-render my page so that the original property(shifts) will now have the filtered data and this means any change in the search input should update my data object. The snippet below works perfectly so that when I monitor the logged variable filteredData I can see its returning the expected data. When I type on the search input the data is filtered as expected and when I clear the search, the object contains the data in the original shifts property.
The issue occurs when I assign this filtered data to my original object i.e. this.shifts=filteredData. When I do this, the shifts property will contain the filtered data but when I clear the search the previously filtered data is what will still be assigned meaning that the shifts property is not being properly updated. Not sure why this is happening.
new Vue({
el: "#app",
data: {
search_input: '',
shifts: {"John":[{"user_id":193,"shift_hours":0}],"Rose":[{"user_id":194,"shift_hours":0}]},
},
methods: {
searchInput() {
const filteredData = Object.keys(this.shifts).reduce(
(obj, key) => {
if (
key.toLowerCase().includes(this.search_input.toLowerCase())
) {
obj[key] = this.shifts[key];
}
return obj;
},
{}
);
console.log(filteredData);
}
}
})
<script src="https://cdnjs.cloudflare.com/ajax/libs/vue/2.5.17/vue.js"></script>
<div id="app">
<input v-model="search_input" #input.prevent="searchInput" type="text"/>
</div>
I've appended an additional snippet below to showcase the issue I'm facing:
new Vue({
el: "#app",
data: {
search_input: '',
shifts: {"John":[{"user_id":193,"shift_hours":0}],"Rose":[{"user_id":194,"shift_hours":0}]},
},
methods: {
searchInput() {
const filteredData = Object.keys(this.shifts).reduce(
(obj, key) => {
if (key.toLowerCase().includes(this.search_input.toLowerCase())) {
obj[key] = this.shifts[key];
}
return obj;
},
{}
);
this.shifts = filteredData;
}
}
})
<script src="https://cdnjs.cloudflare.com/ajax/libs/vue/2.5.17/vue.js"></script>
<div id="app">
<input v-model="search_input" #input.prevent="searchInput" type="text" />
<pre>{{ shifts }}</pre>
</div>
Data needs to be a function, and you can use computed property for filtering:
new Vue({
el: "#app",
data() {
return {
search_input: '',
shifts: {"John": [{"user_id": 193, "shift_hours": 0}], "Rose": [{"user_id": 194, "shift_hours": 0}]},
}
},
computed: {
searchInput() {
return Object.keys(this.shifts).reduce((obj, key) => {
if (key.toLowerCase().includes(this.search_input.toLowerCase())) {
obj[key] = this.shifts[key]
}
return obj
}, {} )
}
}
})
<script src="https://cdnjs.cloudflare.com/ajax/libs/vue/2.5.17/vue.js"></script>
<div id="app">
<input v-model="search_input" type="text" />
<pre>{{ searchInput }}</pre>
</div>

Why is the Vue.js input value not updating?

I have a Vue.js text-input component like the following:
<template>
<input
type="text"
:id="name"
:name="name"
v-model="inputValue"
>
</template>
<script>
export default {
props: ['name', 'value'],
data: function () {
return {
inputValue: this.value
};
},
watch: {
inputValue: function () {
eventBus.$emit('inputChanged', {
type: 'text',
name: this.name,
value: this.inputValue
});
}
}
};
</script>
And I am using that text-input in another component as follows:
<ul>
<li v-for="row in rows" :key="row.id">
<text-input :name="row.name" :value="row.value">
</text-input>
</li>
</ul>
Then, within the JS of the component using text-input, I have code like the following for removing li rows:
this.rows = this.rows.filter((row, i) => i !== idx);
The filter method is properly removing the row that has an index of idx from the rows array, and in the parent component, I can confirm that the row is indeed gone, however, if I have, for example, two rows, the first with a value of 1 and the second with a value of 2, and then I delete the first row, even though the remaining row has a value of 2, I am still seeing 1 in the text input.
Why? I don't understand why Vue.js is not updating the value of the text input, even though the value of value is clearly changing from 1 to 2, and I can confirm that in the parent component.
Maybe I'm just not understanding how Vue.js and v-model work, but it seems like the value of the text input should update. Any advice/explanation would be greatly appreciated. Thank you.
You cannot mutate values between components like that.
Here is a sample snippet on how to properly pass values back and forth. You will need to use computed setter/getter. Added a button to change the value and reflect it back to the instance. It works for both directions.
<template>
<div>
<input type="text" :id="name" v-model="inputValue" />
<button #click="inputValue='value2'">click</button>
</div>
</template>
<script>
export default {
props: ['name', 'value'],
computed: {
inputValue: {
get() {
return this.value;
},
set(val) {
this.$emit('updated', val);
}
}
}
}
</script>
Notice that the "#updated" event updates back the local variable with the updated value:
<text-input :name="row.name" :value="row.value" #updated="item=>row.value=item"></text-input>
From your code you are trying to listen to changes.. in v-model data..
// Your Vue components
<template>
<input
type="text"
:id="name"
:name="name"
v-model="inputValue"
>
</template>
<script>
export default {
props: ['name', 'value'],
data: function () {
return {
inputValue: ""
};
},
};
</script>
If You really want to listen for changes..
<ul>
<li v-for="row in rows" :key="row.id">
<text-input #keyup="_keyUp" :name="row.name" :value="row.value">
</text-input>
</li>
</ul>
in your component file
<template>...</template>
<script>
export default {
props: ['name', 'value'],
data: function () {
return {
inputValue: ""
};
},
methods : {
_keyUp : () => {// handle events here}
};
</script>
check here for events on input here
To bind value from props..
get the props value, then assign it to 'inputValue' variable
it will reflect in tthe input element

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>

how to see changes in new data generated in a vue component?

Well I hope to explain, I'm generating this data from a component, when I click the checkbox changes in the generated data are not reflected, but when clicking the button with a data already in the instance changes are made, I appreciate if you explain Why or do they have a solution?
this my code
js
Vue.component('fighters', {
template: '#fighters-template',
data() {
return {
items: [
{ name: 'Ryu' },
{ name: 'Ken' },
{ name: 'Akuma' }
],
msg: 'hi'
}
},
methods: {
newData() {
this.items.forEach(item => {
item.id = Math.random().toString(36).substr(2, 9);
item.game = 'Street Figther';
item.show = false;
});
this.items.push()
},
greeting() {
this.msg = 'hola'
}
}
});
new Vue({
el: '#app'
})
html
<main id="app">
<fighters></fighters>
</main>
<template id="fighters-template">
<div class="o-container--sm u-my1">
<ul>
<li v-for="item in items">
<input type="checkbox" v-model="item.show">
{{ item.name }}</li>
</ul>
<button class="c-button c-button--primary" #click="newData()">New Data</button>
<h2>{{ msg }}</h2>
<button class="c-button c-button--primary" #click="greeting()">Greeting</button>
<hr>
<pre>{{ items }}</pre>
</div>
</template>
this live code
https://jsfiddle.net/cqx12a00/1/
Thanks for you help
You don't declare the show variables that your checkboxes are bound to, so they are not reactive – Vue is not aware when one is updated.
It should be initialized like so:
items: [
{ name: 'Ryu', show: false },
{ name: 'Ken', show: false },
{ name: 'Akuma', show: false }
]
You might think that newData would fix it, since it assigns a show member to each item, but Vue cannot detect added properties so they're still not reactive. If you initialized the data as I show above, then the assignment would be reactive.
If you want to add a new reactive property to an object, you should use Vue.set.

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>

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