Actions

Actions define what happens when a user interacts with a widget. Perry supports multiple action types, including a powerful Closure transpilation system that converts PHP closures into native code.

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Simple Actions

Pre-built action types for common operations:

use Perry\UI\Action;
use Perry\UI\Binding;

$display = new Binding('display', '0');

// SetValue — assign a value
$action = Action::set($display, '42');
$action = Action::set($display, true);     // bool
$action = Action::set($display, 3.14);    // float

// Append — concatenate a string
$action = Action::append($display, '1');   // display += "1"

// Clear — reset to initial value
$action = Action::clear($display);         // display = "0"

// Custom — raw platform-specific code (passed through as-is)
$action = Action::custom('display.text = ""');

Widget Actions

Interactive widgets support Action for event handling:

use Perry\UI\Action;
use Perry\UI\Binding;
use Perry\UI\Widget\Button;
use Perry\UI\Widget\Slider;
use Perry\UI\Widget\TextInput;
use Perry\UI\Widget\Toggle;

$display = new Binding('display', '0');

// Button — action on click
$btn = new Button('7', Action::append($display, '7'));

// Slider — action on value change
$slider = new Slider(0, 100, step: 1,
    onChange: Action::set($display, '50'));

// TextInput — action on text change
$input = new TextInput($display,
    onChange: Action::set($display, ''));

// Toggle — action on toggle
$toggle = new Toggle(true,
    onToggle: Action::set($display, 'toggled'));

Supported Events

Widget	Event Property	Description
Button	action (constructor)	Fires on click/tap
Slider	onChange	Fires when value changes
TextInput	onChange	Fires when text changes
Toggle	onToggle	Fires when checked state changes
Checkbox	onChange	Fires when checked state changes
Dropdown	onChange	Fires when selection changes

Action Types by Widget

ActionType	Button	Slider	TextInput	Toggle
SetValue	✅	✅	✅	✅
Append	✅	—	—	—
Clear	✅	—	—	—
Custom	✅	✅	✅	✅
Closure	✅	✅	✅	✅

---

Closure Actions (AST Transpilation)

The most powerful action type. Write PHP closures that get parsed into an AST and cross-compiled to any target language.

use Perry\UI\Action;
use Perry\UI\Binding;

$display = new Binding('display', '0');
$operand1 = new Binding('operand1', 0.0);
$operation = new Binding('operation', '');

$action = Action::fromClosure(
    function () use ($display, $operand1, $operation) {
        $operand1 = floatval($display);
        $operation = '+';
        $display .= '+';
    }
);

How It Works

PHP closure
    ↓ nikic/php-parser
PHP AST
    ↓ Perry\IR\AstToIrVisitor
Perry IR (54 node types)
    ↓ Perry\Generator\{Swift,JavaScript,Kotlin,Dart,CSharp}Generator
Target language code

Closure Bindings (Parameter Substitution)

// Pass external values into the closure at definition time
$action = Action::fromClosure(
    function () use ($display, $digit) {
        $display .= $digit;
    },
    ['digit' => '5']  // $digit is replaced with "5" in generated code
);

// Generated Swift: display = display + "5"
// Generated JS:    state.display = state.display + "5"

Nested Closure Pattern

Use this for parameterized button factories:

function numBtn(string $digit, Binding $display): Button {
    return new Button($digit, Action::fromClosure(
        function () use ($digit, $display) {
            $display .= $digit;
        },
        compact('digit')
    ));
}

$row = new HStack(
    numBtn('1', $display),
    numBtn('2', $display),
    numBtn('3', $display),
);

---

Supported PHP Features

Feature	Swift	JavaScript	Kotlin	Dart	C#
Variables	var x	let x	var x	var x	var x
State vars	x = ...	state.x = ...	x.value = ...	x.value = ...	x = ...
If/else	if {} else {}	if {} else {}	if {} else {}	if {} else {}	if {} else {}
While	while {}	while {}	while {}	while {}	while {}
For	for {}	for {}	for {}	for {}	for {}
Foreach	for x in y	for x of y	for x in y	for x in y	foreach x in y
Ternary	c ? a : b	c ? a : b	if (c) a else b	c ? a : b	c ? a : b
Switch	switch {}	switch {}	when {}	switch {}	switch {}
Match	match {}	switch+return	when->	switch+IIFE	switch expr
Try/catch	do{}catch{}	try{}catch{}	try{}catch{}	try{}catch{}	try{}catch{}
Throw	throw	throw	throw	throw	throw
Type cast	Int(), Double()	parseInt(), parseFloat()	.toInt(), .toDouble()	int.parse(), double.parse()	(int), (double)
Increment	+= 1	x++	x++	x++	x++
Compound assign	+=, -=, *=, /=	✅	✅	✅	✅
Nullsafe	?.method()	?.method()	?.method()	?.method()	?.method()
Static call	Class.method()	Class.method()	Class.method()	Class.method()	Class.method()

---

PHP Function Mappings

97+ PHP built-in functions are mapped across all 5 target languages:

PHP	Swift	JavaScript	Kotlin	Dart	C#
substr($s, -1)	String(s.last!)	s.slice(-1)	s.last().toString()	s[s.length-1]	s[s.Length-1]
substr($s, 0, -1)	String(s.dropLast(1))	s.slice(0,-1)	s.dropLast(1)	s.substring(0,s.length-1)	s.Substring(0,s.Length-1)
substr($s, 1)	String(s.dropFirst(1))	s.slice(1)	s.dropFirst(1)	s.substring(1)	s.Substring(1)
strlen($s)	s.count	s.length	s.length	s.length	s.Length
floatval($x)	Double(x) ?? 0	parseFloat(x)	x.toDoubleOrNull() ?: 0.0	double.parse(x.toString())	Convert.ToDouble(x)
intval($x)	Int(x)	parseInt(x)	x.toIntOrNull() ?: 0	int.parse(x.toString())	Convert.ToInt32(x)
strval($x)	String(x)	String(x)	x.toString()	x.toString()	x.ToString()
in_array($x, $a)	a.contains(x)	a.includes(x)	a.contains(x)	a.contains(x)	a.Contains(x)
strpos($s, $n)	s.firstIndex(of: n)	IIFE with indexOf	s.indexOf(n)	s.indexOf(n)	s.IndexOf(n)
end($a)	a.last!	a[a.length-1]	a.last()	a.last	a[a.Length-1]
number_format($n,$d)	String(format: "%.$df", $n)	n.toFixed(d)	String.format("%.$df",n)	n.toStringAsFixed(d)	$n.ToString("F$d")
floor($x)	floor(x)	Math.floor(x)	Math.floor(x).toInt()	x.floor()	Math.Floor(x)
empty($x)	x.isEmpty	!x	x.isEmpty()	x.isEmpty	string.IsNullOrEmpty(x)
count($a)	a.count	a.length	a.size	a.length	a.Length
json_decode($s)	JSONDecoder()	JSON.parse(s)	Gson().fromJson(...)	jsonDecode(s)	JsonConvert.DeserializeObject(...)
json_encode($v)	JSONEncoder()	JSON.stringify(v)	Gson().toJson(...)	jsonEncode(v)	JsonConvert.SerializeObject(...)
preg_match($p, $s)	range(of: p, in: s)	s.match(p)	p.toRegex().find(s)	s.contains(RegExp(p))	Regex.IsMatch(s, p)
array_push($a, $v)	a.append(v)	a.push(v)	a.add(v)	a.add(v)	a.Add(v)
array_reduce($a, $f)	a.reduce(0, f)	a.reduce(f)	a.reduce(f)	a.reduce(f)	a.Aggregate(f)
array_unique($a)	Array(Set(a))	[...new Set(a)]	a.distinct()	a.toSet().toList()	a.Distinct().ToArray()
array_merge($a, $b)	a + b	[...a, ...b]	a + b	[...a, ...b]	a.Concat(b)

=== false optimization: All generators detect expr === false and emit !expr instead.