.notNull

The .notNull rule is used to ensure that the value of a given property is not null (including undefined by default, though this is configurable).

tip

If you only want to check for undefined values, you may use the .notUndefined rule instead.

Examples

Default Usage

If you don't specify any options, the rule will check that the given value is not null or undefined.

In other words, the includeUndefined option is defaulted to true - this decision was made to avoid introducing a breaking change.

In this setup, both null and undefined values will be considered invalid.

import { Validator } from 'fluentvalidation-ts';

type FormModel = {
  customerId?: number | null;
};

class FormValidator extends Validator<FormModel> {
  constructor() {
    super();

    this.ruleFor('customerId').notNull();
  }
}

const formValidator = new FormValidator();

formValidator.validate({ customerId: 100 });
// ✔ {}

formValidator.validate({ customerId: null });
// ❌ { customerId: 'Value cannot be null' }

formValidator.validate({ customerId: undefined });
// ❌ { customerId: 'Value cannot be null' }

formValidator.validate({});
// ❌ { customerId: 'Value cannot be null' }

Excluding undefined

The behaviour of the .notNull rule can be made "strict" (in the sense that it only checks for null and not undefined) by passing the includeUndefined option as false.

In this setup, undefined values will be allowed, and only null values will be considered invalid.

import { Validator } from 'fluentvalidation-ts';

type FormModel = {
  customerId?: number | null;
};

class FormValidator extends Validator<FormModel> {
  constructor() {
    super();

    this.ruleFor('customerId').notNull({ includeUndefined: false });
  }
}

const formValidator = new FormValidator();

formValidator.validate({ customerId: 100 });
// ✔ {}

formValidator.validate({ customerId: null });
// ❌ { customerId: 'Value cannot be null' }

formValidator.validate({ customerId: undefined });
// ✔ {}

formValidator.validate({});
// ✔ {}

Reference

.notNull(ruleOptions?: NotNullRuleOptions)

A validation rule which ensures that the given property is not null (or undefined, depending on the value of ruleOptions).

The default value of ruleOptions is { includeUndefined: true }, meaning that both null and undefined values will be considered invalid.

NotNullRuleOptions

Equivalent to { includeUndefined: boolean }, where the includeUndefined property determines whether undefined values should be considered invalid.

When includeUndefined is true, both null and undefined values will be considered invalid.

When includeUndefined is false, only null values will be considered invalid, and undefined values will be allowed.

Example Message

Value cannot be null