FormController class

Controller for managing form state, validation, and submission.

The FormController coordinates all form field interactions, maintaining a centralized registry of field values and validation states. It provides programmatic access to form data collection, validation triggering, and submission handling.

The controller automatically manages the lifecycle of form fields as they register and unregister, tracking their values and validation results. It supports both synchronous and asynchronous validation, cross-field validation dependencies, and comprehensive error state management.

Example:

final controller = FormController();

// Listen to form state changes
controller.addListener(() {
  print('Form validity: ${controller.isValid}');
  print('Form values: ${controller.values}');
});

// Submit the form
await controller.submit();

// Access specific field values
final emailValue = controller.getValue(emailKey);