How can you update ngModel in Angular and mark the form as dirty or invalid programmatically?

Question

How can you update ngModel in Angular and mark the form as dirty or invalid programmatically?

My form is connected to a model as shown below

In the component file:

myTextModel: string;
updateMyTextModel(): void {
    this.myTextModel = "updated model value";
    //todo- set form dirty (or invalid or touched) here
}

Html template:

<form #testForm="ngForm" id="testForm">
  <input type="text" id="myText" [(ngModel)]="myTextModel" name="myText" #myText="ngModel">
</form>
<button (click)="updateMyTextModel()">Update myTextModel</button>
<div *ngIf="testForm.dirty">testForm dirty</div>
<div *ngIf="testForm.touched">testForm touched</div>

I am looking for a way to programmatically mark the form as touched or dirty. How can I achieve this?

Please note: Although in this example a button is used to update the model, it could also be updated through other means like a callback from an asynchronous web API request.

angular typescript angular4-forms

Answer 1

Answer №1

Solution:

//In this code snippet, we have the root app component in Angular.

import {Component, NgModule, VERSION} from '@angular/core'
import {BrowserModule} from '@angular/platform-browser'
import { Component, ViewChild } from '@angular/core';
import { FormsModule }   from '@angular/forms';

@Component({
  selector: 'my-app',
  template: `
    <form #testForm="ngForm" id="testForm">
        <input type="text" id="myText" [(ngModel)]="myTextModel" name="myText" #myText="ngModel">
    </form>
    <button (click)="updateMyTextModel()">Update myTextModel</button>
    <div *ngIf="testForm.dirty">testForm diry</div>
    <div *ngIf="testForm.touched">testForm touched</div>
  `,
})
export class App {

  @ViewChild('testForm') test: any;

  updateMyTextModel(){
    this.test.control.markAsTouched();
    this.test.control.markAsDirty();

  }

  constructor() {
    console.log(this.test);
  }
}

@NgModule({
  imports: [ BrowserModule,FormsModule ],
  declarations: [ App ],
  bootstrap: [ App ]
})
export class AppModule {}

Plunkr working:

https://plnkr.co/edit/YthHCEp6iTfGPVcNr0JF?p=preview

Answer 2

Solution:

//In this code snippet, we have the root app component in Angular.

import {Component, NgModule, VERSION} from '@angular/core'
import {BrowserModule} from '@angular/platform-browser'
import { Component, ViewChild } from '@angular/core';
import { FormsModule }   from '@angular/forms';

@Component({
  selector: 'my-app',
  template: `
    <form #testForm="ngForm" id="testForm">
        <input type="text" id="myText" [(ngModel)]="myTextModel" name="myText" #myText="ngModel">
    </form>
    <button (click)="updateMyTextModel()">Update myTextModel</button>
    <div *ngIf="testForm.dirty">testForm diry</div>
    <div *ngIf="testForm.touched">testForm touched</div>
  `,
})
export class App {

  @ViewChild('testForm') test: any;

  updateMyTextModel(){
    this.test.control.markAsTouched();
    this.test.control.markAsDirty();

  }

  constructor() {
    console.log(this.test);
  }
}

@NgModule({
  imports: [ BrowserModule,FormsModule ],
  declarations: [ App ],
  bootstrap: [ App ]
})
export class AppModule {}

Plunkr working:

https://plnkr.co/edit/YthHCEp6iTfGPVcNr0JF?p=preview

Answer 3

Answer №2

Why not consider utilizing Reactive forms like FormGroup?

let testForm = new FormGroup({
    myText: new FormControl('initial value')
})

<form [formGroup]="testForm">
    <input type="text" formControlName="myText">
</form>

<button (click)="updateMyTextModel()">Update myTextModel</button>
<div *ngIf="testForm.dirty">testForm dirty</div>
<div *ngIf="testForm.touched">testForm touched</div>

You can use the markAsDirty() method within your function based on specific conditions.

updateMyTextModel(): void {
    this.myTextModel = "updated model value";
    if ( // some condition ) {
        this.testForm.markAsDirty();
    }
}

To mark individual form controls as dirty or touched, you can do the following:

this.testForm.get('myText').markAsDirty();
this.testForm.get('myText').markAsTouched();

Answer 4

Why not consider utilizing Reactive forms like FormGroup?

let testForm = new FormGroup({
    myText: new FormControl('initial value')
})

<form [formGroup]="testForm">
    <input type="text" formControlName="myText">
</form>

<button (click)="updateMyTextModel()">Update myTextModel</button>
<div *ngIf="testForm.dirty">testForm dirty</div>
<div *ngIf="testForm.touched">testForm touched</div>

You can use the markAsDirty() method within your function based on specific conditions.

updateMyTextModel(): void {
    this.myTextModel = "updated model value";
    if ( // some condition ) {
        this.testForm.markAsDirty();
    }
}

To mark individual form controls as dirty or touched, you can do the following:

this.testForm.get('myText').markAsDirty();
this.testForm.get('myText').markAsTouched();

Answer 5

Answer №3

Here is a suggested solution:

@ViewChild('exampleForm') exampleForm;


updateTextModel(): void {
    this.textModel = "new value for model";
    this.form.example.markAsDirty();
}

Answer 6

Here is a suggested solution:

@ViewChild('exampleForm') exampleForm;


updateTextModel(): void {
    this.textModel = "new value for model";
    this.form.example.markAsDirty();
}

Answer 7

Answer №4

When utilizing the NgForm form reference in this manner -

@ViewChild('viewChildForm') public viewChildForm: NgForm;

and attempting to change the form programmatically in the .ts file:

To mark the form as invalid:

this.viewChildForm.form.setErrors({ 'invalid': true });

.

To mark the form as valid:

this.viewChildForm.form.setErrors(null);

Answer 8

When utilizing the NgForm form reference in this manner -

@ViewChild('viewChildForm') public viewChildForm: NgForm;

and attempting to change the form programmatically in the .ts file:

To mark the form as invalid:

this.viewChildForm.form.setErrors({ 'invalid': true });

.

To mark the form as valid:

this.viewChildForm.form.setErrors(null);

Answer 9

Answer №5

To iterate through all input fields within a form and set them as touched or dirty, you can use the following code:

onSubmit(formName)
{
    let inputArray = formName.form.controls;
    for(let key in inputArray)
    {
        inputArray[key].markAsTouched();
        inputArray[key].markAsDirty();
    }
}

Answer 10

To iterate through all input fields within a form and set them as touched or dirty, you can use the following code:

onSubmit(formName)
{
    let inputArray = formName.form.controls;
    for(let key in inputArray)
    {
        inputArray[key].markAsTouched();
        inputArray[key].markAsDirty();
    }
}

How can you update ngModel in Angular and mark the form as dirty or invalid programmatically?

Answer №1

Answer №2

Answer №3

Answer №4

Answer №5

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