requiredUnless

The field is required unless a sibling field matches a trigger condition. The complement of requiredIf.

Signature

NguardValidators.CrossField.requiredUnless(
    fieldKey: string,
    value?: primitive,
    isStrict?: boolean,
): ValidatorFn

Parameter	Type	Default	Description
fieldKey	string	—	The key of the sibling field whose value bypasses the requirement
value	primitive (optional)	undefined	If provided, the sibling must equal this value to bypass the requirement
isStrict	boolean	false	If true, the equality check against value is strict (===)

Reactive forms

import { FormControl, FormGroup } from '@angular/forms';
import { NguardValidators } from 'ng-nguard';

// 'state' is required unless 'country' is set to 'US'
new FormGroup({
    country: new FormControl(''),
    state: new FormControl('', [
        NguardValidators.CrossField.requiredUnless('country', 'US'),
    ]),
});

// 'reason' is required unless 'agreedToTerms' is truthy
new FormGroup({
    agreedToTerms: new FormControl(false),
    reason: new FormControl('', [
        NguardValidators.CrossField.requiredUnless('agreedToTerms'),
    ]),
});

Template-driven forms

<!-- Shorthand: required unless 'agreedToTerms' is truthy -->
<input ngModel name="reason" [nguardRequiredUnless]="'agreedToTerms'" />

<!-- Object form: required unless sibling equals a specific value -->
<input
    ngModel
    name="state"
    [nguardRequiredUnless]="{ fieldKey: 'country', value: 'US' }"
/>

<!-- Strict equality against a numeric value -->
<input
    ngModel
    name="taxId"
    [nguardRequiredUnless]="{ fieldKey: 'accountType', value: 1, isStrict: true }"
/>

Error key

{ requiredUnless: true }

Notes

• The rule is bypassed when the sibling matches the trigger; in that case any value — including empty — passes.
• When the trigger value is omitted, any truthy sibling value bypasses the rule.
• When the trigger is provided and isStrict: false (default), == is used — '1' matches 1.
• When the control has no parent form group, the sibling is unreachable so the rule applies and the field's value must be truthy.

See also

• requiredIf — opposite direction