I made some components with mixins.
mixin1.vue
export default {
data(){
return {
$_mixin1_data1 : 'data1',
data2 : 'data2'
}
},
methods:{
$_mixin1_method1(){
}
}
}
Parent.vue
import mixin1 from './mixin1';
export default {
name : 'Parent',
mixins:[mixin1],
data(){
return {
parent1 : 'parent1'
}
},
mounted(){
console.log(this.parent1); // parent1
console.log(this.$_mixin1_data1) //undefined
console.log(this.data2); //data2
}
}
When I use Parent component with mixin1 component, Parent component could not find data that starts with $. But "data2" data and the method that starts with $ is worked. I don't know why the data that starts with $_ isn't detected. I might not understand Vue's concept.
Thanks for your reply.
Docs
Vue uses a $ prefix when exposing its own built-in APIs via the component instance. It also reserves the prefix _ for internal properties. You should avoid using names for top-level data properties that start with either of these characters.
Related
I'm using Vue in vanilla JS and have a property defined in my data of type string which looks like this
data() {
return {
DimensionSetting: { type : String }
}
}
I have an element in my template that I want to toggle off when a value is passed into DimensionSetting however I can't figure out how I need to check for it in the v-if logic. I tried v-if="!this.DimensionSetting" and v-if="this.DimensionSetting === undefined" and v-if="this.DimensionSetting === null". None of these make the element visible when the value is empty. What do I need to do to properly check that kind of property?
It looks like you're incorrectly mixing a data property declaration with a props declaration.
If DimensionSetting is supposed to be a public property that receives values from a parent component, it should be declared under props:
export default {
props: {
DimensionSetting: {
type: String,
}
}
}
On the other hand, if DimensionSetting is supposed to be a local property, private to the component itself, then it should be returned from data(). There is no type field like there is for props declarations:
export default {
data() {
return {
DimensionSetting: ''
}
}
}
In either case, using the ! operator on the prop should be enough to check for an empty string:
<p v-if="!DimensionSetting">Empty</p>
demo
try adding,
data(){
return{
DimensionSetting: { type : String ,default:false}
}
}
and then v-if="!DimensionSetting"
How to work with validations of nested components inside a parent component with Vuelidate? I would like to change parentForm.$invalid if inputs in subcomponents are valid or not.
Parent:
<parent-component>
</child-component-1>
</child-component-2>
</parent-component>
validations: {
parent: WHAT HERE?
}
Child-1
<child-component-1>
</some-input>
</child-component-1>
data() {
return {
someInput: ""
};
},
validations: {
someInput: required
}
Child-2
<child-component-2>
</some-input>
</child-component-2>
data() {
return {
someInput: ""
};
},
validations: {
someInput: required
}
I might not be an expert in Vue.
If you have declared validations in the child component and you want to access it from the parent component you can use reference the child component from parent component in this way.
In parent component it would be like
<template>
<my-child ref="mychild"> </my-child>
</template>
You can access the validations declared in my-child component which is $v object using
this.$refs.mychild.$v
and then you can use validations of child component in parent components with such ease. Hope this will make the job much easier then using complex ways and it worked for me.
The simplest way to get started with vuelidate for sub-components/form is to use Vue.js dependency injection mechanism provided by provide/inject pair. The $v instance created in parent component can be shared with children component.
As you more fine tune it, you can use Vuelidate data-nesting and only pass a subset of $v to your subcomponents. This is a roughly similar approach to how Angular does with nested Forms. It would look something like:
export default {
data() {
return {
form1: {
nestedA: '',
nestedB: ''
} /* Remaining fields */
}
},
validations: {
form1: {
nestedA: {
required
},
nestedB: {
required
}
},
form2: {
nestedA: {
required
},
nestedB: {
required
}
}
}
}
Alternately, you can declare independent instances of $v for each component. In your case, you will have one for parent and two for children. When you hit the submit button, get the reference of child component using $refs and check if nested form within the child component is valid or not.
I am having a data object that consists of properties unrelated to vue/the UI and data that describes the state. Now I only want the state to be reactive but I need the entire object initially in the component. I need that vue not modifies the other properties because it messes with another library accessing the other properties. (expects array but gets observer)
Is it possible to only make part of an object reactive?
class Game {
constructor() {
this.untrackedProperty = ...;
this.state = {
these: "",
should: "",
be: "",
reactive: ""
}
}
}
// vue component
<script>
export default {
data: function() {
return {
gameState: null
}
},
created() {
this.game = new Game();
this.gameState = this.game.state;
}
}
</script>
Something like that.
I meant it as "That's how I think it should work - it doesn't, but I think it describes pretty well my intentions"
How about passing into your component 2 values:
state this will be tracked
untrackedProperty this will not be tracked
Instead of passing Game as a whole object, separate those 2 values
Codepen Demo
I have a component which has an location object as props. The argument I passed in is locations[index] which is a selected item from a locations array.
However, the component cannot react when the index change. As you can see in the demo, the JSON change as you click the button, but the component cannot update.
What's the best way to make the component reactive?
Your location component populates the province and city data properties in the mounted hook only. When the location prop changes, the mounted hook will not be called again, so you are left with stale data.
Use a computed property instead:
computed: {
province() {
return this.location.province;
},
city() {
return this.location.city;
}
}
Updated codepen
If you really do require province and city to be data properties (and not computed properties) then you will need to watch the location prop to update the properties:
data() {
return {
province: null,
city: null
}
},
watch: {
location: {
immediate: true,
handler(loc) {
this.province = loc.province;
this.city = loc.city;
}
}
}
Nested items in your prop location won't be reactive, you'll need to use something like lodash deepClone :
<location :location.sync="_.deepClone(loc)"></location>
That's it, no need for watchers or anything else.
How do I access $refs inside computed? It's always undefined the first time the computed property is run.
Going to answer my own question here, I couldn't find a satisfactory answer anywhere else. Sometimes you just need access to a dom element to make some calculations. Hopefully this is helpful to others.
I had to trick Vue to update the computed property once the component was mounted.
Vue.component('my-component', {
data(){
return {
isMounted: false
}
},
computed:{
property(){
if(!this.isMounted)
return;
// this.$refs is available
}
},
mounted(){
this.isMounted = true;
}
})
I think it is important to quote the Vue js guide:
$refs are only populated after the component has been rendered, and they are not reactive. It is only meant as an escape hatch for direct child manipulation - you should avoid accessing $refs from within templates or computed properties.
It is therefore not something you're supposed to do, although you can always hack your way around it.
If you need the $refs after an v-if you could use the updated() hook.
<div v-if="myProp"></div>
updated() {
if (!this.myProp) return;
/// this.$refs is available
},
I just came with this same problem and realized that this is the type of situation that computed properties will not work.
According to the current documentation (https://v2.vuejs.org/v2/guide/computed.html):
"[...]Instead of a computed property, we can define the same function as a method. For the end result, the two approaches are indeed exactly the same. However, the difference is that computed properties are cached based on their reactive dependencies. A computed property will only re-evaluate when some of its reactive dependencies have changed"
So, what (probably) happen in these situations is that finishing the mounted lifecycle of the component and setting the refs doesn't count as a reactive change on the dependencies of the computed property.
For example, in my case I have a button that need to be disabled when there is no selected row in my ref table.
So, this code will not work:
<button :disabled="!anySelected">Test</button>
computed: {
anySelected () {
if (!this.$refs.table) return false
return this.$refs.table.selected.length > 0
}
}
What you can do is replace the computed property to a method, and that should work properly:
<button :disabled="!anySelected()">Test</button>
methods: {
anySelected () {
if (!this.$refs.table) return false
return this.$refs.table.selected.length > 0
}
}
For others users like me that need just pass some data to prop, I used data instead of computed
Vue.component('my-component', {
data(){
return {
myProp: null
}
},
mounted(){
this.myProp= 'hello'
//$refs is available
// this.myProp is reactive, bind will work to property
}
})
Use property binding if you want. :disabled prop is reactive in this case
<button :disabled="$refs.email ? $refs.email.$v.$invalid : true">Login</button>
But to check two fields i found no other way as dummy method:
<button :disabled="$refs.password ? checkIsValid($refs.email.$v.$invalid, $refs.password.$v.$invalid) : true">
{{data.submitButton.value}}
</button>
methods: {
checkIsValid(email, password) {
return email || password;
}
}
I was in a similar situation and I fixed it with:
data: () => {
return {
foo: null,
}, // data
And then you watch the variable:
watch: {
foo: function() {
if(this.$refs)
this.myVideo = this.$refs.webcam.$el;
return null;
},
} // watch
Notice the if that evaluates the existence of this.$refs and when it changes you get your data.
What I did is to store the references into a data property. Then, I populate this data attribute in mounted event.
data() {
return {
childComps: [] // reference to child comps
}
},
methods: {
// method to populate the data array
getChildComponent() {
var listComps = [];
if (this.$refs && this.$refs.childComps) {
this.$refs.childComps.forEach(comp => {
listComps.push(comp);
});
}
return this.childComps = listComps;
}
},
mounted() {
// Populates only when it is mounted
this.getChildComponent();
},
computed: {
propBasedOnComps() {
var total = 0;
// reference not to $refs but to data childComps array
this.childComps.forEach(comp => {
total += comp.compPropOrMethod;
});
return total;
}
}
Another approach is to avoid $refs completely and just subscribe to events from the child component.
It requires an explicit setter in the child component, but it is reactive and not dependent on mount timing.
Parent component:
<script>
{
data() {
return {
childFoo: null,
}
}
}
</script>
<template>
<div>
<Child #foo="childFoo = $event" />
<!-- reacts to the child foo property -->
{{ childFoo }}
</div>
</template>
Child component:
{
data() {
const data = {
foo: null,
}
this.$emit('foo', data)
return data
},
emits: ['foo'],
methods: {
setFoo(foo) {
this.foo = foo
this.$emit('foo', foo)
}
}
}
<!-- template that calls setFoo e.g. on click -->