element验证根据条件决定是否是必填项

示例：

			<el-form-item label="删除工单任务:" prop="deleteSheetno" :rules="this.formData.businessType === '1040'?rules.deleteSheetno:[{ required: false, message: '请输入要删除的工单任务号', trigger: 'blur' }]">
			<el-row class="demo-autocomplete">
                    <el-col :span="12">
                        <el-autocomplete
                        class="inline-input"
                        v-model="inputState"
                        :fetch-suggestions="querySearch"
                        placeholder="请输入或选择要删除的工单任务"
                        @select="handleSelectSheet"
                        ></el-autocomplete>
                    </el-col>
                </el-row>
			 </el-form-item>

其实关键代码只有绑定的rule;如下：:rules=“this.formData.businessType === ‘1040’?rules.deleteSheetno:[{ required: false, message: ‘请输入要删除的工单任务号’, trigger: ‘blur’ }]”，这里的值this.formData.businessType === ‘1040’，可根据是字符串或者数字决定等于什么或者不等于什么；如果等于，就是必填的，如果不等于，那就不是必填的。