级联 select，如何设置当第一个select变化时触发清空第二个select的值，valueTemplate好像没有效果

[leo0o]

作者你好，我想要当第一个下拉框发生变化时，第二个框能自动清空内容，但是现在情况是，只有在第二个框刚加载出来的时候，值会被初始化，其他时候第二个框就不会再跟随变化了，请问是我设置的有问题吗，代码如下：

{
  "type": "object",
  "properties": {
    "data": {
      "type": "array",
      "ui": {
        "widget": "array-table",
        "widgetConfig": {},
        "columns": 12,
        "showLabel": true,
        "noLabelSpace": false,
        "showLegend": false,
        "disabled": false,
        "readonly": false,
        "hidden": false,
        "help": {
          "show": false,
          "text": "?"
        },
        "linkFields": []
      },
      "rules": {},
      "items": {
        "type": "object",
        "items": {},
        "properties": {
          "type": {
            "type": "string",
            "ui": {
              "widget": "select",
              "widgetConfig": {
                "enumSource": [
                  {
                    "label": "A",
                    "value": "A"
                  },
                  {
                    "label": "B",
                    "value": "B"
                  }
                ]
              },
              "columns": 12,
              "showLabel": true,
              "noLabelSpace": false,
              "showLegend": false,
              "disabled": false,
              "readonly": false,
              "hidden": false,
              "help": {
                "show": false,
                "text": "?"
              },
              "linkFields": []
            },
            "rules": {}
          },
          "subtype": {
            "type": "string",
            "ui": {
              "widget": "select",
              "widgetConfig": {
                "enumSource": "dx: {{$const}}[{{$root.data[i].type}}]"
              },
              "columns": 12,
              "showLabel": true,
              "noLabelSpace": false,
              "showLegend": false,
              "disabled": false,
              "readonly": false,
              "hidden": false,
              "help": {
                "show": false,
                "text": "?"
              },
              "linkFields": []
            },
            "rules": {
              "customRule": []
            },
            "valueTemplate": "0",
            "base": {
              "key": "subtype",
              "type": "string",
              "valueTemplate": "0"
            }
          }
        }
      },
      "base": {
        "key": "data",
        "type": "array",
        "items": {
          "type": "object",
          "items": {},
          "properties": [
            {
              "type": "string",
              "ui": {
                "widget": "select",
                "widgetConfig": {
                  "enumSource": [
                    {
                      "label": "A",
                      "value": "A"
                    },
                    {
                      "label": "B",
                      "value": "B"
                    }
                  ]
                },
                "columns": 12,
                "showLabel": true,
                "noLabelSpace": false,
                "showLegend": false,
                "disabled": false,
                "readonly": false,
                "hidden": false,
                "help": {
                  "show": false,
                  "text": "?"
                },
                "linkFields": []
              },
              "rules": {},
              "key": "type"
            },
            {
              "type": "string",
              "ui": {
                "widget": "select",
                "widgetConfig": {
                  "enumSource": "dx: {{$const}}[{{$root.data[i].type}}]"
                },
                "columns": 12,
                "showLabel": true,
                "noLabelSpace": false,
                "showLegend": false,
                "disabled": false,
                "readonly": false,
                "hidden": false,
                "help": {
                  "show": false,
                  "text": "?"
                },
                "linkFields": []
              },
              "rules": {
                "customRule": []
              },
              "valueTemplate": "0",
              "base": {
                "key": "subtype",
                "type": "string",
                "valueTemplate": "0"
              },
              "key": "subtype"
            }
          ]
        }
      }
    }
  },
  "root": true,
  "globalConfig": {
    "ignoreRulesWhenHidden": true,
    "style": {},
    "css": {},
    "constants": {
      "A": [
        {
          "label": "a1",
          "value": "a1"
        },
        {
          "label": "a2",
          "value": "a2"
        }
      ],
      "B": [
        {
          "label": "b1",
          "value": "b1"
        },
        {
          "label": "b2",
          "value": "b2"
        }
      ]
    },
    "scrollToFailField": {
      "enabled": false
    }
  },
  "checked": false,
  "ui": {
    "widgetConfig": {}
  }
}

[daniel-dx]

最近比较忙，问题跟进得比较慢，见谅哈

你的问题可以通过尝试这个设置 selectFirstItem: false

{
  multiple: false, // Whether to choose more
  clearable: true, // Whether the empty button appears
  filterable: false, // Whether searchable
  filterLocal: true, // Filter by local or remote data. if true, even with enumSourceRemote, data will only be retrieved once remotely.
  size: '', // Size. Options：[medium | small | mini]

  itemDataKey: "", // The key of the selected item's data, can accessed by {{$temp[itemDataKey]}}

  itemTemplate: '<span>{{item.label}} : {{item.value}}</span>', // Display item template
  itemLabelField: 'label', // Item data represents the field of the label
  itemValueField: 'value', // Item data represents the field of value
  enumSource: [{value: [String | Number | Boolean], label: ''}], // Local data source
  enumSourceRemote: { // Remote data source
    remoteUrl: '', // If it is remote call, fill in the url
    paramName: 'keyword', // Request parameter name, default is keyword
    otherParams: {}, // Additional request parameters.
    resField: '', // Response result field
    selectFirstItem: false // Whether the first item is selected by default
  },
}

[leo0o]

作者你好，由于这个数据读取的是全局 $const 里面的，设置 selectFirstItem 可能没用，试过确实没效果。

[luqiudi]

作者你好，由于这个数据读取的是全局 $const 里面的，设置 selectFirstItem 可能没用，试过确实没效果。

你好，我想问下，你这个用dx表达式写在enumSource属性里面形成前后级联的这种形式行得通么

[luqiudi]

作者你好，由于这个数据读取的是全局 $const 里面的，设置 selectFirstItem 可能没用，试过确实没效果。

你可以试试在valuetemplate后边跟一个函数来处理一下清空这个逻辑
我现在试了下，
这个可以生效
return ($root.ClassesList.list[0].value] || [])
但是下面这个空数组并不能生效，太奇怪了，也就是说，可以在第一个下拉改变的情况下，更改第二个下拉选择的值。但是并不能给他清空