vue 根据下拉框动态切换form的rule

taskCategorySelect (val) {  // 任务类别下拉选择
  if ( val == 5 ) {
    this.cameraORgateway = false;  // true不可以使用  = 不可以使用
    this.cameraORgatewayCP = true;
    this.rules.gatewayCode = [{ required: true, message: '请选择关联网关', trigger: 'blur' }];
    this.rules.cameraCode = [{}];
    this.$refs['form'].clearValidate('cameraCode');
    this.form.cameraCode = undefined;
  } else if ( val == 1 || val == 2 || val == 3 || val == 4) {
    this.cameraORgateway = true;  // false不可以使用  = 可以使用
    this.cameraORgatewayCP = false;
    this.rules.cameraCode = [{ required: true, message: '请选择摄像机', trigger: 'blur' }];
    this.rules.gatewayCode = [{}];
    this.form.gatewayCode = undefined;
  } else {
    this.cameraORgateway = true;
    this.cameraORgatewayCP = true;
    this.form.cameraCode = undefined;
    this.form.gatewayCode = undefined;
  }
},