public FormStateInterface::setCompleteForm(array &$comple

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::unsetValue($key)

public FormStateInterface::setError(array &$element, $message

public FormStateInterface::isCached()

public FormStateInterface::hasFileElement()

public FormStateInterface::setMethod($method)

public &FormStateInterface::getValue($key, $default = NULL)

public FormStateInterface::getValidateHandlers()

public FormStateInterface::setProcessInput($process_input = TRUE)