Validation Rules

Every rule is one decorator, imported from its own file (@system-inc/base-foundation/validation/decorators/<Name>). This is the full built-in catalog.

Type checks

@VerifyIsString() · @VerifyIsNumber() · @VerifyIsInt() · @VerifyIsBoolean() · @VerifyIsDate() · @VerifyIsObject() · @VerifyIsArray() · @VerifyIsDefined() · @VerifyIsEnum(EnumOrValues)

Ranges and lengths

• @VerifyMin(n) / @VerifyMax(n): numeric bounds (inclusive).
• @VerifyMinLength(n) / @VerifyMaxLength(n): string length bounds.
• @VerifyLength(min, max?): combined length bounds.
• @VerifyMinDate(date) / @VerifyMaxDate(date): date bounds.

Formats

• @VerifyIsEmail() · @VerifyIsUrl() · @VerifyIsDomain() · @VerifyIsUUID(version?) · @VerifyIsIP(version?)
• @VerifyIsPhoneNumber(options?): E.164, NANP, or international.
• @VerifyIsCountryCode(format?): alpha-2, alpha-3, or numeric.
• @VerifyIsLocale() · @VerifyIsTimeZone()
• @VerifyStringMatches(pattern): regex.

Presence and emptiness

• @VerifyIsNotEmpty(): rejects null, undefined, '', [], and {}. Numbers (including 0), booleans, and class instances are never "empty."
• @VerifyIsOptional() — the opt-out sentinel: marks a field as allowed to be absent, so other rules on it only run when a value is present.

Array rules

Most rules run per element when placed on an array field. A few operate on the array itself:

• @VerifyArrayMinSize(n) / @VerifyArrayMaxSize(n): element count bounds.
• @VerifyArrayUnique(): no duplicate elements.
• @VerifyIsArray(): the value is an array at all.
• @VerifyIsNotEmpty() is also array-level by design: on an array field it checks the array (an empty array fails), not each element.

@VerifyArrayMinSize(1)
@VerifyArrayUnique()
@SerializableField(() => [String])
tags: string[];

Rules double as predicates

Every rule carries a standalone .check() you can call anywhere, outside any decorator:

import { VerifyIsEmail } from '@system-inc/base-foundation/validation/decorators/VerifyIsEmail';
import { VerifyLength } from '@system-inc/base-foundation/validation/decorators/VerifyLength';

VerifyIsEmail.check('ada@example.com'); // true
VerifyLength.check('hi', 3, 10); // false

Handy for imperative checks in services — same rule, same semantics, no duplicate logic.

Need a rule that doesn't exist? Write your own — the built-ins are all made with the same public builder.