用js引用子组件方法不能使用

changeImg:function(food){
var v_show=food.show;
this.goods.forEach(e=>{
if(!!e.petCardList){
e.petCardList.forEach(x=>{
if(x.id==food.id){
_self.$refs.cartcontrol.add(x);
x.show = !v_show;
}
})
}
});