vue下拉選擇select option多選取值問題

 <el-select v-model="rolePost" multiple  filterable allow-create default-first-option placeholder="請選擇" @change="change">
     <el-option
      v-for="item in rolePosts"
      :value="item.id"
      :label="item.postName"
      :key="item.id" >

      </el-option>
</el-select>

 var vm = new Vue({
            el: "#app",
            data: {
               rolePosts:[
                    {id:6, postName: "名稱1"},
                    {id:7, postName: "名稱2"},
                    {id:8, postName: "名稱3"}
               ],
               rolePost:[],
               id:0  
            },
            methods: {
                change:function(){
                    console.log(this.rolePost)
                },
            }

        })

粗陋代碼，望您指導