从子组件向父组件发出值

Question

In my Nuxt.js application, I try to emit a value from child to parent component.

The parent component is: pages/index.vue :

<template>
  <div>
    <custom-input v-model="value" />
    <v-btn @click="showValue">
      Ok
    </v-btn>
  </div>
</template>

<script>
import CustomInput from '@/components/CustomInput.vue'
export default {
  components: { CustomInput },
  data () {
    return {
      value: 'hello'
    }
  },
  watch: {
    value (val) {
      console.log('value' + val)
    }
  },
  methods: {
    showValue () {
      console.log('value is: ' + this.value)
    }
  }
}
</script>

The child is: component/CustomInput.vue :

<template>
  <v-text-field
    v-bind:value="value"
    v-on:input="$emit('input', value)"
  />
</template>

<script>
export default {
  name: 'CustomInput',
  props: {
    value: {
      type: String,
      required: true
    }
  },
  watch: {
    value () {
      this.$emit('input', this.value)
    }
  }
}
</script>

When I click on the button Ok, I am not getting the updated value. What am I missing ?

Screenshot shows the new value is not console logged on a button click, instead the old one is displayed.

I followed the official documentation here

Related simple demo is hosted on Github.

Answer 1

This line is wrong:

v-on:input="$emit('input', value)"

This is emitting the old value.

It should be:

v-on:input="$emit('input', $event)"

This will emit the new value.

Alternatively you could use:

v-on:input="value => $emit('input', value)"

Or move it out to a method in methods .