1. 商品数量增减

2. 用深度监听同步到本地存储

src/pages/cart/cart.vue

@@ -7,9 +7,9 @@
       <goodsItem :item="item" />
       <!-- 3. 计数器 -->
       <view class="count">
-        <view class="count_btn iconfont icon-jianshao"></view>
+        <view @tap="itemChangeCount(index, -1)" class="count_btn iconfont icon-jianshao"></view>
         <text class="count_text">{{ item.goods_count }}</text>
-        <view class="count_btn iconfont icon-zengjia"></view>
+        <view @tap="itemChangeCount(index, 1)" class="count_btn iconfont icon-zengjia"></view>
       </view>
     </view>
 
@@ -47,8 +47,34 @@ export default {
 
         // 判断全选
          this.selectAll = this.cartList.every(item=>item.goods_select === true)
+      },
+
+      // 商品数量的增减
+      itemChangeCount(index, num){
+          // 如果数量为1 , 并且还减少, 提示删除商品
+          if(this.cartList[index].goods_count === 1 && num === -1){
+            wx.showModal({
+                content: '是否删除该商品',
+                success: (res) => {
+                    if (res.confirm) {
+                        this.cartList.splice(index, 1)
+                    }
+                }
+            })
+            return
+          }
+          this.cartList[index].goods_count += num
       }
   },
+  //深度监听
+  watch: {
+      cartList: {
+          deep: true,
+          handler(val){
+              uni.setStorageSync("cartList", val)
+          }
+      }
+  }
 }
 </script>