Provides an interface for an object containing the current state of a form. This is passed to all form related code so that the caller can use

public FormStateInterface::hasValue($key)

public &FormStateInterface::getUserInput()

public &FormStateInterface::getStorage()

public FormStateInterface::setRedirect($route_name, array $route_parameters

public FormStateInterface::isProcessingInput()

public FormStateInterface::cleanValues()

public FormStateInterface::getButtons()

public FormStateInterface::isExecuted()

public FormStateInterface::getRebuildInfo()