微信小程序购物车-多商家-多商品

 data: {
    shops: {},           //商品
    curt: 0,             //分类id
    curindex: 0,         //当前index
    idx: 0,
    ishow: 1,
    cai: [],             //菜的数组
    allprice: 0,        //总家
    allnum: 0          //总商品数
  },

 onLoad: function (options) {
    let id = options.id;
    //商家详情本地请求资源
    wx.showToast({
      title: '成功',
      duration: 500,
      success: (e) => {
        if (e.errMsg === 'showToast:ok') {
          this.setData({
            shops: data.shops[id],
            cai: data.shops[id].cai
          })
          console.log(this.data.cai)
        } else {
          console.log(e.errMsg)
        }
      }
    })
  }

        <view class='left-nav'>
          <view wx:for="{{shops.lefttitle}}">
            <view class="shops-left-title {{curt == item.id ? 'bg' : ''}}" catchtap="goIndex" data-id="{{item.id}}" data-index="{{index}}">
              <text class='t'>{{item.lefttitle}}</text>
            </view>
          </view>
        </view>

<scroll-view scroll-y class='scroll'>
          <view class='cai'>
            <!--一句curt来显示不是菜 curt===分类id-->
            <view wx:for="{{cai[curt]}}" wx:for-item="cai" wx:for-index="caiindex">
              <!--具体的菜-->
              <view class='right-cai'>
                <image src="{{cai.img}}"></image>
                <view class='middle'>
                  <text>{{cai.cainame}}</text>
                  <text class='shou'>月售{{cai.shou}}</text>
                  <text class='price'>￥{{cai.price}}</text>
                </view>
                <!--加减按钮-->
                <view class='btn'>
                  <text class='add' catchtap="minus" data-index="{{caiindex}}" wx:if="{{cai.num===0?false:true}}">-</text>
                  <text class='cainum' wx:if="{{cai.num===0?false:true}}">{{cai.num}}</text>
                  <text class='add' catchtap="add" data-index="{{caiindex}}">+</text>
                </view>
              </view>
            </view>
          </view>
 </scroll-view>

 //增加商品数量
  add(e) {
    let index = e.currentTarget.dataset.index
    let cai = this.data.cai;
    let curt = this.data.curt;//当前是哪个分类下的菜
    let num = cai[curt][index].num;//当前菜的数量
    num++;
    cai[curt][index].num = num //点击后菜的数量
    this.setData({
      cai: cai   //更新菜
    })
    this.getAll() //计算总计
  }

 minus(e) {
    let index = e.currentTarget.dataset.index
    let cai = this.data.cai;
    let curt = this.data.curt;//当前是哪个分类下的菜
    let num = cai[curt][index].num;
    if (num <= 0) {
      return false;
    }
    num--;
    //重新赋值数量
    cai[curt][index].num = num
    this.setData({
      cai: cai
    })
    this.getAll()
  }

  //计算总价
  getAll() {
    let cai = this.data.cai;
    let total = 0;
    let allnum = 0;
    let allcainame=""
    //循环当前类别菜数组
    for (let i = 0; i < cai.length; i++) {
      let c = cai[i];
      for (let j = 0; j < c.length; j++) {
        let num = c[j].num
        let price = c[j].price;
        //计算总商品数        
        allnum += num
         //计算总价
        total += num * price
      }
    }
    this.setData({
      allprice: total,
      allnum: allnum
    });
  },

 //跳转支付页面
  getAllprice() {
    // console.log(this.data.shops)
    //传递菜馆名，总价
    let title = this.data.shops.title;
    let allprice = this.data.allprice;
    let cainame = this.data.cainame;
    if (this.data.allnum === 0) {
      wx.showModal({
        title: '商品为空！',
        content: '您选择商品了吗？',
      })
      return
    } else {
      //商品数量不能为0
      this.getAll()
      wx.navigateTo({
        url: '../pay/pay?allprice=' + allprice + '&title=' + title 
      })
    }
  }