Storyblok fieldtype with field validation

Fieldtype.js

const Fieldtype = {
  mixins: [window.Storyblok.plugin],
  template: `<div>
  <input class="uk-width-1-1" @input="validate" v-model="proxyModel.example" />
  <div v-if="!valid">Please fill out this field</div>
</div>`,
  data() {
    return {
      proxyModel: {},
      valid: false
    }
  },
  methods: {
    initWith() {
      return {
        
      }
    },
    validate() {
      if (this.proxyModel.example.length > 3) {
        this.valid = true
        this.$emit('changed-model', this.proxyModel)
      } else {
        this.valid = false
        this.$emit('changed-model', {})
      }
    },
    pluginCreated() {
      if (this.model !== {}) {
        this.proxyModel = this.model
      }
      console.log('plugin:created')
    }
  }
}