Validate a required boolean in Vue

Useful when making sure checkboxes have been ticked

2020-04-25
frontend
vue
vuelidate

Required booleans

Let’s say you have a checkbox that you need your users to click/check before proceeding —like accepting some ToS or agreeing to something.

This falls on the realm of form validation, and there is nothing better than Vuelidate for that.

If you already know some Vuelidate you might be tempted to go with something like:

<!-- template... -->

<script>
import { required } from 'vuelidate/lib/validators'

export default {
  data () {
    return {
      hasAccepted: false
    }
  },

  validations: {
    hasAccepted: { required }
  }
}
</script>

But you just can’t use the required validator on a checkbox —or switch.

That’s because it’s a boolean.

The model for those would contain a boolean value, true or false, and either would make the validation pass since those values are different from other values the model can contain, such as null or undefined.

What we need to check here, is whether the value of the model is equal to true or not.

Let’s do something like this instead:

<!-- template... -->

<script>
// import { required } from 'vuelidate/lib/validators'

export default {
  data () {
    return {
      hasAccepted: false
    }
  },

  validations: {
    hasAccepted: {
      accepted: val => val === true
    }
  }
}
</script>

Source code

Here is the source code for a working example:

<template lang="pug">
.simple-required-boolean-good.mb-8
  v-card
    v-card-title Example #2
    v-card-text
      v-switch(
        v-model="$v.hasAccepted.$model"
        :error="$v.hasAccepted.$error"
        :hint="hintText"
        label="Do you accept?"
        persistent-hint
      )
      v-checkbox(
        v-model="$v.hasAccepted.$model"
        :error="$v.hasAccepted.$error"
        :hint="hintText"
        label="Do you accept?"
        persistent-hint
      )
</template>


<script>
export default {
  data () {
    return {
      hasAccepted: false
    }
  },

  computed: {
    hintText () {
      const value = `value: ${this.hasAccepted}`
      const invalid = `invalid: ${this.$v.hasAccepted.$invalid}`
      const error = `error: ${this.$v.hasAccepted.$error}`

      return `${value} -> ${invalid} -> ${error}`
    }
  },

  validations: {
    hasAccepted: {
      accepted: val => val === true
    }
  }
}
</script>

That’s it! :sunglasses: