如何根据 Angular 11 中 html 代码处的条件使反应式表单字段成为必填字段

Question

我的表单中有两个 select/dropdown 字段，第二个下拉字段根据条件 *ngIf="selectedStdntList?.packages" 呈现。但是在下面的代码中，它会停止提交表单，即使条件 *ngIf="selectedStdntList?.packages" 不成立并且第二个下拉菜单没有呈现在屏幕上。

学生-list.component.html

<form [formGroup]="moveStudentForm" #formDirective="ngForm" (ngSubmit)="moveStudent();">
    <uitk-form-field>
      <label uitkLabel>Student List:</label>
      <uitk-select id="my-required-reactive-select" formControlName="stdntListCtrl"
        [itemList]="stdntListDropdown" [showError]="moveStudentForm?.controls?.stdntListCtrl?.errors?.required"
        defaultLabel="Please Select" defaultLabelFlag="true">
      </uitk-select>
      <uitk-form-field-error
        *ngIf="moveStudentForm?.controls?.stdntListCtrl?.errors?.required && moveStudentForm?.controls?.stdntListCtrl?.touched">
        <span>Please select student list</span>
      </uitk-form-field-error>
    </uitk-form-field>


    <uitk-form-field *ngIf="selectedStdntList?.packages">
      <label uitkLabel>Package:</label>
      <uitk-select id="my-required-reactive-select" formControlName="moveStudentPackageCtrl" [itemList]="packagesDropdown"
        [showError]="moveStudentForm?.controls?.packageCtrl?.errors?.required" defaultLabel="Please Select"
        defaultLabelFlag="true">
      </uitk-select>
      <uitk-form-field-error
        *ngIf="moveStudentForm?.controls?.packageCtrl?.errors?.required && moveStudentForm?.controls?.packageCtrl?.touched">
        <span>Please select package</span>
      </uitk-form-field-error>
    </uitk-form-field>
</form>

学生-list.component.ts

    @Component({
        selector: 'stdnt-list',
        templateUrl: './stdnt-list.component.html',
        styleUrls: ['./stdnt-list.component.scss']
    })
    export class StdntListComponent implements OnInit {
        
        stdntListDropdown: IUITKSelectItemProps[] = [];
        moveStudentForm: FormGroup;
    
        constructor(private dataService: DataService)
            
            this.moveStudentForm = new FormGroup({
                stdntListCtrl: new FormControl(null, Validators.required),
                moveStudentPackageCtrl: new FormControl(null, Validators.required),
            });
        }
    
        ngOnInit() {
            this.stdntList = this.dataService.loadStudentData();
        }
        
        moveStudent() {
            ...
        }
    }

期望输出：

如果第二个字段条件 *ngIf="selectedStdntList?.packages" 为真，那么只有该字段的验证器应该工作，否则只有第一个字段验证器应该工作并且应该允许提交表单。

Answer 1

要使 formControl“不验证”，您有两个选择：创建自定义验证器或禁用 FormControl

创建自定义验证器类型“requiredIf”。创建自定义验证器有一个问题，即在条件更改时需要 UpdateValueAndValiddity FormControl。在中，它使用垫输入的事件（更改）。我不知道你的“uitk-select”是否有事件（变化）或类似的（*）

要在正常输入中禁用 formControl，您不能使用 [disabled]，否则您需要使用指令（例如 ), or, again, if your "uitk-select" has an [disable] property or you can use the event (change) to disabled the formControl -using the methods enable and disabled-。但在这种情况下重要你需要使用

[style.display]="!selectedStdntList?.packages?'none':null"

不是 *ngIf

(*)当您使用非标准库时，请注明您使用的库帮助我们帮助您。

Answer 2

您可以根据 selectedStdntList 值动态设置验证器。

    this.moveStudentForm = new FormGroup({
      stdntListCtrl: new FormControl(null, Validators.required),
      moveStudentPackageCtrl: new FormControl(null)
    });
    
    // Need to add/clear validator based on selectedStdntList?.packages value dynamically
    // Not sure how are you using 'selectedStdntList' in StdntListComponent
    // Below code should be executed whenever 'selectedStdntList' value changes
    
    const moveStudentPackageCtrl = this.moveStudentForm.get('moveStudentPackageCtrl');
    if (this.selectedStdntList?.packages) {
      // set validators - PS: this will clear previous Validators if any, and only set the ones specified here
      moveStudentPackageCtrl?.setValidators(Validators.required);
    } else {
      // clear validator
      moveStudentPackageCtrl?.clearValidators();
    }
    moveStudentPackageCtrl?.updateValueAndValidity();

作为替代设置和清除验证器的替代方法，您甚至可以动态添加或删除表单控件moveStudentPackageCtrl：

    this.moveStudentForm = new FormGroup({
      stdntListCtrl: new FormControl(null, Validators.required)
    });
    
    
    // Add/remove control based on selectedStdntList?.packages value dynamically
    // Not sure how are you using 'selectedStdntList' in StdntListComponent
    // Below code should be executed whenever 'selectedStdntList' value changes
    
    if (this.selectedStdntList?.packages) {
      this.moveStudentForm.addControl('moveStudentPackageCtrl', new FormControl(null, Validators.required));
    } else {
      this.moveStudentForm.removeControl('moveStudentPackageCtrl');
    }

如何根据 Angular 11 中 html 代码处的条件使反应式表单字段成为必填字段

How to make reactive form fields mandatory based on condition at html code in Angular 11

typescript

angular

angular11