Forms

About

AngularAngular

guide/forms

Angular will not automatically detect the inputs and selects.

Angular injects a couple of classes on the inputs and selects.

Best Practices

• Mainly use Reactive forms.

• Use FormBuilder service to be able to use Typed FormControls by default.

  • It will thought create FormControls with Type | null.

• To avoid having nullable types, use NonNullableFormBuilder service.

Details

Foundation Classes

FormControl

Tracks the value and validation status of an individual form control (input).

Its parameters are (in order):

1. The initial value.

2. Array of Validators.

3. Array of async Validators.

FormGroup

Defines a form with a fixed set of form controls that you can manage together.

Its parameters are (in order):

1. Object of multiple FormControl, FormGroup or FormArray.

FormArray

Defines a dynamic form, where you can add and remove controls at run time.

ControlValueAcessor

Creates a bridge between Angular FormControl instances and built-in DOM elements.

Control States

These are classes added to the element, so you can define custom CSS for them.

The form itself will also receive these state classes.

• ng-touched: The control has been visited, even clicked (had focus on).

• ng-untouched: The control hasn't been visited yet.

• ng-dirty: The control's value has been changed.

• ng-pristine: The control's value hasn't been changed.

• ng-valid: The control's value is valid.

• ng-invalid: The control's value isn't valid.

ngForm

ngForm has a submitted value on the <form>, after you <form #thisForm="ngForm">, that is useful if you want to display error only after the form has been submit.

Resetting the Form

You can reset the form values and states by calling .reset() method.

• You may provide as parameter values to be used.

• Otherwise it will the the initial values as default.

But these will only reset the groups and controls validations and values.

To reset the #form itself from have been submitted you will have to:

1. Provide the <form #thisForm="ngForm"> with a Local Template Reference.

2. Access the reference with a viewChild() or access it on the (ngSubmit)="handleSubmit(thisForm)" function.

3. Call resetForm() of ngForm on the variable, this will reset the submitted of the form to false again.