interface
An interface implemented by classes that perform synchronous validation.
interface Validator { validate(control: AbstractControl): ValidationErrors | null registerOnValidatorChange(fn: () => void)?: void }
validate() | |||
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Method that performs synchronous validation against the provided control. | |||
|
control | AbstractControl | The control to validate against. |
ValidationErrors | null
: A map of validation errors if validation fails, otherwise null.
registerOnValidatorChange() | |||
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Registers a callback function to call when the validator inputs change. | |||
|
fn | () => void | The callback function |
void
The following example implements the Validator
interface to create a validator directive with a custom error key.
@Directive({ selector: '[customValidator]', providers: [{provide: NG_VALIDATORS, useExisting: CustomValidatorDirective, multi: true}] }) class CustomValidatorDirective implements Validator { validate(control: AbstractControl): ValidationErrors|null { return {'custom': true}; } }
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https://v10.angular.io/api/forms/Validator