在mutations中注冊(cè)的setCart方法：//store.js mutations：{    setCart(state,foodIndex){         Vue.set(state.goods.foods[foodIndex],"count",1);     } }組件中提交mutations并使用setCart方法//childComponent.vuemethods:{     setCart(foodIndex){                 this.$store.commit('setCart',this.foodIndex);           },     },               addCartItem:function (event) {             if (!this.food.count){                  this.setCart(this.foodIndex);         }else{                   this.addCart(this.foodIndex)                    return         }       },結(jié)果會(huì)報(bào)錯(cuò)，this.foodIndex is undefined ，在created中console了this.foodIndex，結(jié)果正常，我直接傳數(shù)值給setCart：this.addCart(0)依然會(huì)報(bào)錯(cuò)：this.foodIndex is undefined會(huì)不會(huì)我在store.js注冊(cè)的mutations方法不對(duì)？