How can Vue.js use the v-if directive for events?

Question

How can Vue.js use the v-if directive for events?

Is it possible to react to an event within a vue template? For example, if a child component dispatches an event like $dispatch('userAdded'), can I display a message in the parent component based on that?

<div class="alert alert-info" v-if="userAdded">
    User was created!
</div>

If not, is there a way to access variables from the child component instead?

<div class="alert alert-info" v-if="$refs.addView.form.successful">
    User was created!
</div>

I've tried both approaches without success.

Also, while we're on the subject, is there a clean way to automatically hide elements after a certain amount of time? Perhaps something like this (to hide after 2 seconds):

<div class="alert alert-info" v-if="$refs.addView.form.successful" hide-after="2000">
    User was created!
</div>

Thank you!

edit: I've created my own hide-after directive:

Vue.directive('hide-after', {
  update: function(value) {
    setTimeout(() => this.el.remove(), value);
  }
});

<div class="alert alert-info" v-hide-after="2000">
    This will be shown for 2 seconds
</div>

javascript vue.js

Answer 1

Answer №1

A solution would be to follow these steps if you want to achieve it.

Start by creating a child component that dispatches an event.
In the parent component, set up an event listener for the event and create a data property that will be updated by the event listener on the component instance.
Bind the v-if of the parent component to the local data property created in step 2.

The code implementation would resemble something like this:

Parent Component

HTML

<div v-if="showAlert"></div>

Javascript

events: {
  'alert.show': function () {
    this.showAlert = true
  },
  'alert.hide': function () {
    this.showAlert = false
  }
},
data () {
  return {
    showAlert: false
  }
}

Child Component

Javascript

methods: {
  showAlert (show) {
    show ? this.$dispatch('alert.show') : this.$dispatch('alert.hide')
  }
}

It is recommended to avoid using $child and $parent as it creates tight coupling between components making the child less modular.

The dispatch method bubbles up until it reaches a listener, allowing multiple nested components to control the alert state.

UPDATE

Alternatively, if you prefer not using events, you can establish a two-way binding property in the child component which can be updated by either the parent or child component.

Example:

Parent Component

HTML

<div v-if="showAlert"></div>
<child-component :show-alert.sync="showAlert"></child-component>

Javascript

data () {
  return {
    showAlert: false
  }
}

Child Component

Javascript

props: {
  showAlert: {
    type: Boolean,
    twoWay: true
  }
},
methods: {
  showAlertInParent (show) {
    this.$set('showAlert', show)
  }
}

Answer 2

A solution would be to follow these steps if you want to achieve it.

Start by creating a child component that dispatches an event.
In the parent component, set up an event listener for the event and create a data property that will be updated by the event listener on the component instance.
Bind the v-if of the parent component to the local data property created in step 2.

The code implementation would resemble something like this:

Parent Component

HTML

<div v-if="showAlert"></div>

Javascript

events: {
  'alert.show': function () {
    this.showAlert = true
  },
  'alert.hide': function () {
    this.showAlert = false
  }
},
data () {
  return {
    showAlert: false
  }
}

Child Component

Javascript

methods: {
  showAlert (show) {
    show ? this.$dispatch('alert.show') : this.$dispatch('alert.hide')
  }
}

It is recommended to avoid using $child and $parent as it creates tight coupling between components making the child less modular.

The dispatch method bubbles up until it reaches a listener, allowing multiple nested components to control the alert state.

UPDATE

Alternatively, if you prefer not using events, you can establish a two-way binding property in the child component which can be updated by either the parent or child component.

Example:

Parent Component

HTML

<div v-if="showAlert"></div>
<child-component :show-alert.sync="showAlert"></child-component>

Javascript

data () {
  return {
    showAlert: false
  }
}

Child Component

Javascript

props: {
  showAlert: {
    type: Boolean,
    twoWay: true
  }
},
methods: {
  showAlertInParent (show) {
    this.$set('showAlert', show)
  }
}

Answer 3

Answer №2

Events are a crucial concept in programming as they allow you to respond dynamically. However, it is important that these reactions are centralized through the model rather than scattered throughout different parts of your codebase. The use of $dispatch is no longer recommended. Instead, here's how you can achieve this:

Within the child component, trigger an event like this:

this.$emit('didIt' {wasItAwful:'yep',wereYouScared:'absolutely'});

In the parent component, set up the event listener using v-on within the child component's tag...

<adventure-seeking-child v-on:did-it='myChildDidIt' />

Next, in the parent's methods section, define the handler function.

methods : { myChildDidIt : function(payload){ ... } }

You can find more information in the official documentation.

Answer 4

Events are a crucial concept in programming as they allow you to respond dynamically. However, it is important that these reactions are centralized through the model rather than scattered throughout different parts of your codebase. The use of $dispatch is no longer recommended. Instead, here's how you can achieve this:

Within the child component, trigger an event like this:

this.$emit('didIt' {wasItAwful:'yep',wereYouScared:'absolutely'});

In the parent component, set up the event listener using v-on within the child component's tag...

<adventure-seeking-child v-on:did-it='myChildDidIt' />

Next, in the parent's methods section, define the handler function.

methods : { myChildDidIt : function(payload){ ... } }

You can find more information in the official documentation.

How can Vue.js use the v-if directive for events?

Answer №1

Answer №2

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