Validated<T extends Object?> class sealed

Represents the result of validation: either Valid or Invalid.

Validated is similar to Result but specifically designed for validation use cases where you may need to collect multiple errors instead of failing fast on the first error. This makes it ideal for form validation where users want to see all problems at once, rather than fixing them one by one.

Use Validated when:

• You need to collect multiple validation errors together
• You want a fluent, chainable validation API
• You're validating forms or complex objects with many rules
• You want users to see all validation problems simultaneously

Use Result instead when:

• You only care about a single error, not accumulation
• You need fail-fast behavior
• You're handling operations with typed errors

Example:

// Collect all validation errors at once
final validation = check(name, (n) => n.isNotEmpty, error: 'Required')
  .check((n) => n.length >= 3, error: 'Too short')
  .check((n) => n.length <= 50, error: 'Too long');

if (validation.isValid) {
  processName(validation.unwrapOrNull()!);
} else {
  // Show all errors to the user
  final errors = (validation as Invalid).errors.toList();
}