when function

IValidator when(IValidator condition, { required IValidator then, required IValidator otherwise, String? message, })

Creates a conditional validator. It's conditional based on some other field in the eskema.

The condition validator is run against the parent map.

• If the condition is met, then is used to validate the current field's value.
• If the condition is not met, otherwise is used.

Usage Examples:

// Conditional validation based on user type
final userValidator = eskema({
  'userType': $isString,
  'permissions': when(
    isEq('admin'),           // Condition: if userType is 'admin'
    isList(),                // Then: permissions must be a list
    isEq(null),              // Otherwise: permissions must be null
  ),
});

// Age-based validation
final personValidator = eskema({
  'age': $isInt,
  'licenseNumber': when(
    isGte(18),               // Condition: if age >= 18
    stringLength([isEq(8)]), // Then: license must be 8 characters
    isEq(null),              // Otherwise: license must be null
  ),
});

// Complex conditional logic
final paymentValidator = eskema({
  'method': $isString,
  'cardNumber': when(
    isEq('credit_card'),     // If payment method is credit card
    stringMatchesPattern(r'^\d{16}$'), // Then: validate 16-digit card number
    isEq(null),              // Otherwise: card number should be null
  ),
});

Implementation

IValidator when(
  IValidator condition, {
  required IValidator then,
  required IValidator otherwise,
  String? message,
}) {
  final base = WhenValidator(condition: condition, then: then, otherwise: otherwise);

  // Wrap with a proxy that intercepts misuse (validate()) and parent usage (validateWithParent)
  return message == null ? base : WhenWithMessage(base, message);
}