vue：props中的值賦值給data

父組件：

<template>
	<div>
		<navbar :ctype="ctype"></navbar>
	</div>
</template>

<script>
import navbar from '@/components/navbar'
   export default {
   	components: {navbar},
   	data () {
   		return{
   			ctype:1
   		}
   	}
   }
</script>

子組件：

<template>
	<div>
		<div>{{thistype}}</div>
	</div>
</template>

<script>
export default {
    props:['ctype'],
    computed: {
      normalizedSize: function () {
        return this.ctype.trim().toLowerCase()
      }
    },
    data(){
        return{
            thistype:this.ctype
        }
    }
}
</script>