通过一个很常用的场景来展示vue数据驱动的应用

　　需求：可以动态增减组合条件来进行数据查询。

　　界面运行效果如下图所示：

　　界面第一次加载时，默认会显示一个空的查询条件，如下图所示：

　　

　　点击“加”图标，可以无限增加查询条件，也可以点击“减”图标删除新增的查询条件，如下图所示：

　　

　　说明：第一个下拉框的数据变化时，第三个下拉框的数据要进行联动，第三个组件可以是下拉框也可以是文本框，它是根据第一个下拉框的数据来决定的。第二个下拉框是固定的四个选项>、<、=、!=。如下图所示：

　　

　　定义数据结构：

{
    "data": {
        "array": [{
            "opts": [{
                "val": "0",
                "name": "停止"
            }, {
                "val": "1",
                "name": "运行"
            }],
            "paramCode": "runStatus",
            "name": "运行状态"
        }, {
            "opts": [{
                "val": "0",
                "name": "否"
            }, {
                "val": "1",
                "name": "是"
            }],
            "paramCode": "alarmStatus",
            "name": "报警与否"
        }, {
            "opts": [{
                "val": "0",
                "name": "就地"
            }, {
                "val": "1",
                "name": "远程"
            }],
            "paramCode": "remoteLocal",
            "name": "远程就地"
        }, {
            "opts": [{
                "val": 0,
                "name": "禁用"
            }, {
                "val": 1,
                "name": "启用"
            }],
            "paramCode": "startUse",
            "name": "是否启用"
        }, {
            "opts": [{
                "val": "0",
                "name": "变频"
            }, {
                "val": "1",
                "name": "工频"
            }],
            "paramCode": "runMode",
            "name": "工频启停"
        }, {
            "opts": [{
                "val": 0,
                "name": "手动"
            }, {
                "val": 1,
                "name": "自动"
            }],
            "paramCode": "controlMode",
            "name": "控制模式"
        }, {
            "opts": [{
                "val": "0",
                "name": "手动"
            }, {
                "val": "1",
                "name": "自动"
            }],
            "paramCode": "frequencyMode",
            "name": "频率手自动"
        }, {
            "opts": [],
            "paramCode": "frequencySetValue",
            "name": "频率设定"
        }, {
            "opts": [],
            "paramCode": "frequencyReturnValue",
            "name": "频率反馈"
        }, {
            "opts": [],
            "paramCode": "tempSetValue",
            "name": "温度设定"
        }, {
            "opts": [],
            "paramCode": "tempReturnValue",
            "name": "温度反馈"
        }, {
            "opts": [{
                "val": 0,
                "name": "关"
            }, {
                "val": 1,
                "name": "开"
            }],
            "paramCode": "newWindValveOnOff",
            "name": "新风阀启停"
        }, {
            "opts": [],
            "paramCode": "newWindValveOpen",
            "name": "新风阀开度"
        }, {
            "opts": [],
            "paramCode": "newWindTemp",
            "name": "新风阀温度"
        }, {
            "opts": [],
            "paramCode": "newWindHumidity",
            "name": "新风阀湿度"
        }, {
            "opts": [{
                "val": 0,
                "name": "关"
            }, {
                "val": 1,
                "name": "开"
            }],
            "paramCode": "returnWindValveOnOff",
            "name": "回风阀启停"
        }, {
            "opts": [],
            "paramCode": "returnWindValveOpen",
            "name": "回风阀开度"
        }, {
            "opts": [],
            "paramCode": "returnWindHumidity",
            "name": "回风阀湿度"
        }, {
            "opts": [],
            "paramCode": "co2",
            "name": "回风阀co2"
        }, {
            "opts": [{
                "val": "0",
                "name": "手动"
            }, {
                "val": "1",
                "name": "自动"
            }],
            "paramCode": "waterValveHandAuto",
            "name": "水阀手自动"
        }, {
            "opts": [{
                "val": 0,
                "name": "关"
            }, {
                "val": 1,
                "name": "开"
            }],
            "paramCode": "waterValveOnOff",
            "name": "水阀启停"
        }, {
            "opts": [],
            "paramCode": "waterValveOpenSet",
            "name": "水阀开度设定"
        }, {
            "opts": [],
            "paramCode": "waterValveOpenReturn",
            "name": "水阀开度反馈"
        }, {
            "opts": [],
            "paramCode": "supplyAirTemp",
            "name": "送风温度"
        }, {
            "opts": [],
            "paramCode": "supplyAirHumidity",
            "name": "送风湿度"
        }, {
            "opts": [],
            "paramCode": "supplyAirPressure",
            "name": "送风静压"
        }, {
            "opts": [{
                "val": 0,
                "name": "关"
            }, {
                "val": 1,
                "name": "开"
            }],
            "paramCode": "humidityValveOnOff",
            "name": "加湿阀启停"
        }, {
            "opts": [],
            "paramCode": "humidityValveOpen",
            "name": "加湿阀开度"
        }, {
            "opts": [],
            "paramCode": "filterDiffPressure",
            "name": "过滤网压差"
        }, {
            "opts": [{
                "val": 0,
                "name": "关"
            }, {
                "val": 1,
                "name": "开"
            }],
            "paramCode": "elecHeatOnOff",
            "name": "电加热"
        }, {
            "opts": [],
            "paramCode": "power",
            "name": "功率"
        }, {
            "opts": [],
            "paramCode": "runTime",
            "name": "运行时间"
        }, {
            "opts": [],
            "paramCode": "loadPower",
            "name": "供冷负荷"
        }, {
            "opts": [],
            "paramCode": "cold",
            "name": "累计供冷量"
        }, {
            "opts": [{
                "val": 0,
                "name": "正常"
            }, {
                "val": 1,
                "name": "中断"
            }],
            "paramCode": "commuInterrupt",
            "name": "通讯是否正常"
        }]
    },
    "code": 200,
    "msg": "",
    "errors": null
}

　　因为数据量不大，为了提升性能，数据是接口一次性返回的，数据的联动是在内存当中进行数据筛选，从而避免频繁的接口调用。

　　在数据结构当中，当opts属性值为空数组时，第三个组件显示为文本框，否则显示为下拉框，并把opts中的数据作为第三个组件的下拉框内容展示出来。当第三个组件是下拉框时，第二个下拉框只能显示=和!=这两项，如果是文本框时，都可以显示。

　　后端接口需要的查询参数是：

dataListParams: [{paramName: "runStatus", operator: 2, value: "0"}, {paramName: "startUse", operator: 2, value: 0}]

　　接下来，我们定义vue组件中的内容，Dom部分：

        <div class='search-item'>
          <label>组合条件：</label>
        </div>
        <div class="search-item"
             v-for="(paramObj,index) in dataListParams"
             :key="index">
          <!-- 参数名 -->
          <el-select v-model="paramObj.paramName"
                     filterable
                     clearable
                     @change="(e)=>changeParam(e,index)"
                     placeholder="请选择"
                     style="width:100px">
            <el-option v-for="item in paramList"
                       :key="item.paramCode"
                       :label="item.name"
                       :value="item.paramCode"></el-option>
          </el-select>
          <!-- 操作符列表 -->
          <el-select v-model="paramObj.operator"
                     clearable
                     placeholder=""
                     style="width:60px">
            <el-option v-for="(item,sindex) in operatorOptions"
                       :disabled="getDisabled(sindex,index)"
                       :key="item.id"
                       :label="item.name"
                       :value="item.id"></el-option>
          </el-select>
          <!-- 参数值 -->
          <el-select v-if="listOpts[index].length>0"
                     v-model="paramObj.value"
                     filterable
                     clearable
                     placeholder="请选择"
                     style="width:100px">
            <el-option v-for="item in listOpts[index]"
                       :key="item.val"
                       :label="item.name"
                       :value="item.val"></el-option>
          </el-select>
          <el-input v-else
                    v-model="paramObj.value"
                    :clearable="true"
                    placeholder="请输入"
                    style="width:100px"></el-input>

          <span v-if="index==0"
                class="add-where"><i class="iconfont icon-add"
               @click="addWhere"></i></span>
          <span v-else
                class="remove-where"><i class="iconfont icon-shanchu1"
               @click="removeWhere(index)"></i></span>
        </div>

　　js部分：

export default {
  mixins: [indexOptions],
  data () {
    return {
      //操作符列表
      operatorOptions: [
        { id: 0, name: '>' },
        { id: 1, name: '<' },
        { id: 2, name: '=' },
        { id: 3, name: '!=' }
      ],
      //组合条件
      dataListParams: [{ paramName: "", operator: '', value: "" }],
      checkedAll: false, //全选所有
      deviceIds: [],
      listOpts: [[]]//操作列表
    }
  },
  computed: {//筛选参数列表，如果参数列表dataListParams当中有任何一个属性值为空，则不传递
    filterDataListParams () {
      return this.dataListParams.filter(f => { return f.paramName !== "" && f.operator !== "" && f.value !== "" });
    }
  },
  methods: {//获取操作选项启用、禁用
    getDisabled (sindex, index) {
      if (this.listOpts.length > 0 && this.listOpts[index].length > 0) {
        return [0, 1].includes(sindex);
      } else {
        return false;
      }
    },
    //添加组合条件
    addWhere () {
      this.dataListParams.push({ paramName: '', operator: '', value: '' });
      this.listOpts.push([]);
    },
    //移除组合条件
    removeWhere (index) {
      this.dataListParams.splice(index, 1);
      this.listOpts.splice(index, 1);
    },
    //根据参数编码获取操作列表
    getOptsByParamCode (code,) {
      let res = this.paramList.find(f => f.paramCode == code);
      return res ? res.opts : [];
    },
    //参数选项变化
    changeParam (code, index) {
      //变化之前的类型
      let preType = this.listOpts[index].length > 0; //是否下拉框
      let arr = this.getOptsByParamCode(code);
      this.listOpts[index] = arr;
      this.dataListParams[index].value = '';
      //变化之后的类型
      let nextType = arr.length > 0;//是否是下拉框
      //前后类型不一致时，清空操作符
      if (preType != nextType) {
        this.dataListParams[index].operator = '';
      }
    }
  }
};

　　当第一个下拉框选项变化时，如果第三个组件是相同类型（下拉框或文本框），则第二个下拉框的选项不清空，否则清空。

　　只有一组查询条件当中三个选项的值都不为空时，才会把参数传递给后端，所以前端通过计算熟悉filterDataListParams进行了数据过滤。

　　由于数据结构是动态变化的，所以为了保存查询条件的保存状态，下拉框的数据列表项也应当是动态的（数组存储）。

　　最后把filterDataListParams作为参数传递给后端接口就可以了，这是一个很典型的vue动态数据驱动应用。