Form State: Methods Reference

When to Use

Use getValue() for submitted values (sanitized), set()/get() for persistent storage across rebuilds, setTemporaryValue() for single-request data.

Reference: Value Access Methods

Retrieve Values:

Method	Returns	Use Case
`getValues()`	All values (array)	Full form processing
`getValue($key)`	Single value	Specific field access
`getValue(['parent', 'child'])`	Nested value	Nested form elements
`hasValue($key)`	Boolean	Check before access

Sanitization:

getValue() returns sanitized values (safe)
getUserInput() returns raw unsanitized input (UNSAFE - avoid)
Always use getValue() unless specific reason

Modify Values:

Method	Purpose	When
`setValue($key, $value)`	Set single value	Programmatic changes
`setValues($array)`	Set all values	Programmatic submission
`unsetValue($key)`	Remove value	Conditional processing

Reference: Storage Methods (Persistent)

Across Rebuilds:

Method	Purpose	Persistence
`set($property, $value)`	Store data	Until form complete
`get($property)`	Retrieve data	Until form complete
`has($property)`	Check existence	Until form complete
`setStorage($array)`	Set all storage	Until form complete
`getStorage()`	Get all storage	Until form complete

Common Storage Keys:

'step' - Current step number
'step1_data' - Step-specific data
'total_steps' - Total step count
'entity' - Working entity object
'original_values' - For comparison

Reference: Temporary Storage (Single Request)

Single Request Only:

Method	Purpose	Persistence
`setTemporaryValue($key, $value)`	Store temp data	Current request only
`getTemporaryValue($key)`	Get temp data	Current request only
`hasTemporaryValue($key)`	Check temp	Current request only

Use Cases:

UI state (display mode, active tab)
Calculation intermediates
Conditional display logic
Non-persistent workflow state

Reference: Control Flag Methods

Form Behavior:

Method	Effect	When to Use
`setRebuild($bool)`	Prevent submission	AJAX updates, dynamic forms
`isRebuilding()`	Check rebuild state	Conditional logic
`setCached($bool)`	Enable caching	Multi-step forms (REQUIRED)
`isCached()`	Check cache state	Debugging
`setValidationEnforced($bool)`	Force validation	Programmatic submission
`disableRedirect()`	No redirect	AJAX submission
`setResponse($response)`	Custom response	Non-HTML responses

Redirect Methods:

Method	Purpose	Example
`setRedirect($route, $params, $options)`	Route redirect	`setRedirect('node.add', ['node_type' => 'article'])`
`setRedirectUrl($url)`	URL object redirect	`setRedirectUrl(Url::fromRoute(...))`

Reference: Error Handling Methods

Error Management:

Method	Purpose	Phase
`setErrorByName($name, $msg)`	Set field error	Validation
`setError($element, $msg)`	Set element error	Validation
`getErrors()`	Get all errors	After validation
`getError($element)`	Get element error	After validation
`clearErrors()`	Reset errors	Error recovery
`hasAnyErrors()`	Check error state (static)	Conditional logic

Error Setting Best Practices:

// Preferred - by name
$form_state->setErrorByName('field_name', $this->t('Error'));

// When you have element reference
$form_state->setError($form['field'], $this->t('Error'));

// Check before setting
if (!$form_state->hasAnyErrors()) {
  // Conditional logic
}

Reference: Complete Reference

Interface File: /web/core/lib/Drupal/Core/Form/FormStateInterface.php (1160+ lines)

Implementation: /web/core/lib/Drupal/Core/Form/FormState.php