vue下拉选择select option多选取值问题

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

        })

粗陋代码，望您指导