Angular Reactive Form submit and clear validation

问题

I have a reactive form

 <form [formGroup]="secondFormGroup">
      <ng-template matStepLabel>enter items</ng-template>
      <div style="display: flex; flex-direction: column;">
        <mat-form-field>
          <input matInput type="text" placeholder="category"  [(ngModel)]="newItem.CategoryName" formControlName="category"
          />
        </mat-form-field>
        <mat-form-field>
          <input matInput type="text" placeholder="sub category"  [(ngModel)]="newItem.SubCategoryName" formControlName="subCategory"
          />
        </mat-form-field>
        <mat-form-field>
          <input matInput type="text" placeholder="product"  [(ngModel)]="newItem.ProductName" formControlName="name"/>
        </mat-form-field>
        <mat-form-field>
          <input matInput  [(ngModel)]="newItem.Amount" type="number" min="0" placeholder="amount" formControlName="amount"
          />
        </mat-form-field>
        <mat-form-field>
          <input matInput  [(ngModel)]="newItem.Price" type="number" min="0" placeholder="price" formControlName="price"
          />
        </mat-form-field>
        <button mat-raised-button color="primary" (click)="AddNewProduct(newItem)" style="float: left; align-self: flex-end;">submit</button>
      </div>
    </form>

I initialize it like this:

 this.secondFormGroup = this._formBuilder.group({
  category: ['', Validators.required],
  subCategory: ['', Validators.required],
  name: ['', Validators.required],
  amount: ['', Validators.required],
  price: ['', Validators.required]
});

Upon clicking sumbit I call this method:

AddNewProduct(newProduct) {
if (this.secondFormGroup.valid) {
  //add product
  this.secondFormGroup.reset();
 } 
}

After adding the product, I clear the form. However, once the form is cleared, it triggers the validation errors. I want the validation errors to show only when the user clicks submit and the form isn't valid, not when I clear the form after submitting.

How can I fix this?

回答1:

The issue seems to be that the form is marked as submitted after reset is called. If the form is marked as submitted, regardless of whether or not its pristine, the errors will be highlighted.

You'll need to call resetForm instead, which is on the FormGroupDirective:

@ViewChild(FormGroupDirective) formGroupDirective: FormGroupDirective;

this.formGroupDirective.resetForm();

Secondly, you'll need to wrap it in a setTimeout with a timeout of 0, so that the form is submitted before it resets.

setTimeout(() => this.formGroupDirective.resetForm(), 0)

I've tested this in a StackBlitz, and it all seems to work:

https://stackblitz.com/edit/angular-l6xq1d?file=src%2Fapp%2Fapp.component.ts

回答2:

You can easily clear the validators of form using clearValidators()

this.secondFormGroup .clearValidators();
this.secondFormGroup .updateValueAndValidity();

But this will remove the validators from the actual form group, and it will not show errors on form submit from the next time.

Better way to do is :

You could simply use flag on the error template, to display the errors based on form submit/reset. And set/reset the flag accordingly.

public formSubmitted = false;

onSubmit(){
   this.formSubmitted = true;
}

reset(){
   this.formSubmitted = false;
}

template file

<div *ngIf="formSubmitted">
 display errors
</div>

回答3:

If you are using Angular Material inputs, then you can hide error state by setting inputs as untouched. Material input fields shows error status only if input is touched.

So

this.secondFormGroup.markAsUntouched();

should do the trick.

You may have to initiate change detection run after such operation (depends on scenario)

Here you have proof of concept. Input is initially in error state. Dedicated button clears this state untill future input.

https://stackblitz.com/edit/angular-tadkmb?file=src%2Fapp%2Fapp.component.ts

回答4:

This works, try this you need to reset the formDirective otherwise it will not 100% resting the form

Template:

<form 
  ...
  #formDirective="ngForm" 
>

Component:

import { ViewChild, ... } from '@angular/core';
import { NgForm, ... } from '@angular/forms';

export class MyComponent {
 ...
 @ViewChild('formDirective') private formDirective: NgForm;

  constructor(... )

  private someFunction(): void { 
    ...
    formDirective.resetForm();
  }
}

来源：https://stackoverflow.com/questions/51124575/angular-reactive-form-submit-and-clear-validation