combination.vue

<template>
  <input v-model="message">
</template>

<script>
import { mapMutations } from 'vuex'

export default {
  computed: {
    message: {
      get () {
        return this.$store.state.message
      },
      set (val) {
        this.updateMessage({path: 'entry.message', value: val})
      }
    }
  },
  
  methods: {
    ...mapMutations({
      updateMessage: 'UPDATE_MESSAGE'
    })
  }
}
</script>