MinLengthValidator

A directive that adds minimum length validation to controls marked with the minlength attribute. The directive is provided with the NG_VALIDATORS mult-provider list.

See also

• Form Validation

NgModules

• ReactiveFormsModule

• FormsModule

Selectors

• [minlength][formControlName]
• [minlength][formControl]
• [minlength][ngModel]

Properties

Property	Description
@Input()minlength: string	Tracks changes to the the minimum length bound to this directive.

Description

Adding a minimum length validator

The following example shows how to add a minimum length validator to an input attached to an ngModel binding.

<input name="firstName" ngModel minlength="4">

Methods

ngOnChanges()
A lifecycle method called when the directive's inputs change. For internal use only.
ngOnChanges(changes: SimpleChanges): void Parameters changes SimpleChanges A object of key/value pairs for the set of changed inputs. Returns void

validate()
Method that validates whether the value meets a minimum length requirement. Returns the validation result if enabled, otherwise null.
validate(control: AbstractControl): ValidationErrors | null Parameters control AbstractControl Returns ValidationErrors | null

registerOnValidatorChange()
Registers a callback function to call when the validator inputs change.
registerOnValidatorChange(fn: () => void): void Parameters fn () => void The callback function Returns void