How to solve [Vue warn]: Avoid mutating a prop directly since the value will be overwritten on vue.js 2?

Question

My view is like this :

<div class="col-md-8">
    ...
        <star :value="{{ $data['rating'] }}"></star>
    ...
</div>

My star component is like this :

<template>
    <span class="rating" :class='{"disable-all-rating": !!value}'>
        <template v-for="item in items">
            <label class="radio-inline input-star" :class="{'is-selected': ((starValue>= item.value) && starValue!= null)}">
                <input type="radio" class="input-rating" v-model="starValue" @click="rate(item.value)">
            </label>
        </template>
    </span>
</template>
<script>
    export default{
        props: {
            'value': null
        },
        computed: {
            starValue () {
                return this.temp_value
            }
        },
        data(){
            return{
                items: [
                    {value: 5},
                    {value: 4},
                    {value: 3},
                    {value: 2},
                    {value: 1}
                ],
                temp_value: null,
            }
        },
        methods:{
            rate: function (star) {           
               this.$http.post(window.BaseUrl + '/star', {star: star});                         
               this.temp_value = star;                         
            },
        }
    }
</script>

My css is like this :

span.rating {
  direction: rtl;
  display: inline-block;
}

span.rating .input-star {
  background: url("../img/star.png") 0 -16px;
  padding-left: 0;
  margin-left: 0;
  width: 16px;
  height: 16px;
}

span.rating .input-star:hover, span.rating .input-star:hover ~ .input-star {
  background-position: 0 0;
}

span.rating .is-selected{
   background-position: 0 0;
}

span.rating .is-disabled{
   cursor: default;
}

span.rating .input-star .input-rating {
  display: none;
}

When I click the star, there exist error on the console like this :

[Vue warn]: Avoid mutating a prop directly since the value will be overwritten whenever the parent component re-renders. Instead, use a data or computed property based on the prop's value. Prop being mutated: "value" (found in at C:\xampp\htdocs\myshop\resources\assets\js\components\Star.vue)

How can I solve it?

Answer 1

You need to make the computed with a getter and a setter and then use $emit to update the prop e.g:

    computed: {
        starValue:{ 
            get:function () {
                return this.temp_value
            },
            set: function(newValue){
                // $emit is the correct way to update props:
                this.$emit('update:value', newValue);
            }
        }
    }