更改所选选项后将 ngModel 值设置为 null

Question

我有一个表格，其中包含一个 select 选项和一个 div 部分取决于 selected 选项。在 select 选项中，如果我选择 1 例如，将显示输入

component.ts

types : any[] = [
{ value : '1'},
{ value : '2'},
{ value : '3'}
];

createForm = this.fb.group({
firstInput:['',Validators.required],
secondInput:['',Validators.required],
thirdInput:['',Validators.required],
});

component.html

<select class="form-control" [value]="selected"[(ngModel)]="selectedValue">
<option *ngFor="let x of types">{{x.value}}</option>
</select>

<div *ngIf="selectedValue == '1'">
<label for="1" class="control-label">1</label>
<input id="1" class="form-control" type="text" formControlName="firstInput">
</div>

<div *ngIf="selectedValue == '2'">
<label for="2" class="control-label">2</label>
<input id="2" class="form-control" type="text" formControlName="secondInput">
</div>

<div *ngIf="selectedValue == '3'">
<label for="3" class="control-label">3</label>
<input id="3" class="form-control" type="text" formControlName="thirdInput">
</div>

所有字段都是必填项，我的问题是：当我选择“1”时没有填写“1”的输入然后我更改为第二个选择“2”并填写它，我无法提交表单，因为 fielControllName "firstInput" 尽管不可见但还是空的，所以我需要在每次更改时清除 ngModel 的 selected 值（正如我认为的那样）。

Answer 1

所以最初你的表格必须是这样的：

createForm = this.fb.group({
  selectedValue:[null,Validators.required],
  firstInput:[null],
  secondInput:[null],
  thirdInput:[null],
});

您的 HTML 代码：

 <form  [formGroup]="createForm">
    <select class="form-control" formControlName="selectedValue">
     <option *ngFor="let x of types" value="{{x.value}}">{{x.value}}</option>
    </select>

    <div *ngIf="createForm.value.selectedValue== '1'">
     <label for="1" class="control-label">1</label>
     <input id="1" class="form-control" type="text" formControlName="firstInput">
    </div>

    <div *ngIf="createForm.value.selectedValue== '2'">
     <label for="2" class="control-label">2</label>
     <input id="2" class="form-control" type="text" formControlName="secondInput">
    </div>

    <div *ngIf="createForm.value.selectedValue== '3'">
     <label for="3" class="control-label">3</label>
     <input id="3" class="form-control" type="text" formControlName="thirdInput">
    </div>
</form>

那你必须有on change函数：

    OnChange() {
        this.createForm.get('selectedValue').valueChanges.subscribe(
          val => {
            if (val==1) {
              this.createForm.get('firstInput').setValidators([Validators.required]);
              this.createForm.controls['firstInput'].updateValueAndValidity();
              this.createForm.get('secondInput').setValidators([]);
              this.createForm.controls['secondInput'].updateValueAndValidity();
              this.createForm.get('thirdInput').setValidators([]);
              this.createForm.controls['thirdInput'].updateValueAndValidity();
            }
            else if (val==2) {
              this.createForm.get('firstInput').setValidators([]);
              this.createForm.controls['firstInput'].updateValueAndValidity();
              this.createForm.get('secondInput').setValidators([Validators.required]);
              this.createForm.controls['secondInput'].updateValueAndValidity();
              this.createForm.get('thirdInput').setValidators([]);
              this.createForm.controls['thirdInput'].updateValueAndValidity();
            }
           else if (val==3) {
              this.createForm.get('firstInput').setValidators([]);
              this.createForm.controls['firstInput'].updateValueAndValidity();
              this.createForm.get('secondInput').setValidators([]);
              this.createForm.controls['secondInput'].updateValueAndValidity();
              this.createForm.get('thirdInput').setValidators([Validators.required]);
              this.createForm.controls['thirdInput'].updateValueAndValidity();
            }
          }
        )
      }

如果你想让值变为空，你可以使用：

this.createForm.patchValue({
  firstInput:null,
  secondInput:null,
  thirdInput:null,
})

更改所选选项后将 ngModel 值设置为 null

set ngModel value to null after changing selected option

angular-reactive-forms

angular8

requiredfieldvalidator

ngmodel