select tree支持检索树形

 <el-form-item label="备考地区">
            <el-select
              ref="appendixAreas"
              popper-class="selectArea"
              v-model="form.appendixAreas.name"
              placeholder="请选择"
              :filter-method="filterMethod"
              style="height: 100%"
              filterable
              @focus="selectFocus"
              default-first-option
            >
              <el-option
                :label="form.appendixAreas.name"
                :value="form.appendixAreas.name"
              >
                <el-tree
                  ref="tree"
                  :highlight-current="true"
                  :data="citys"
                  node-key="name"
                  :accordion="true"
                  :props="defaultProps"
                  :expand-on-click-node="true"
                  @node-click="nodeClick"
                  :filter-node-method="filterTree"
                >
                </el-tree>
              </el-option>
            </el-select>
          </el-form-item>
 selectFocus (event) {
      this.$refs.tree.filter('');
    },
    filterMethod (query) {
      console.log(query);
      this.$refs.tree.filter(query);
      return true;
    },
    filterTree (value, data) {
      if (!value) return true;
      return data.name.indexOf(value.trim()) !== -1;
    },