Composite Pattern Generator

Creates Composite pattern infrastructure for treating individual objects and compositions uniformly.

When to Use

Scenario	Example
Tree structures	Menus, file systems, organization charts
Part-whole hierarchies	UI components, product categories
Recursive operations	Calculate totals, render trees
Uniform treatment	Same interface for leaf and composite

Component Characteristics

Component Interface

• Defines operations for all objects
• Shared by leaf and composite
• Enables uniform treatment

Leaf

• Represents individual object
• No children
• Implements component operations

Composite

• Contains children (leaf or composite)
• Delegates operations to children
• Implements component operations

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Generation Process

Step 1: Generate Component Interface

Path: src/Domain/{BoundedContext}/

1. {Name}Interface.php — Operations contract

Step 2: Generate Leaf

Path: src/Domain/{BoundedContext}/

1. {Name}Leaf.php — Individual object

Step 3: Generate Composite

Path: src/Domain/{BoundedContext}/

1. {Name}Composite.php — Container for children

Step 4: Generate Tests

1. {ClassName}Test.php — Component behavior verification

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File Placement

Component	Path
Component Interface	src/Domain/{BoundedContext}/
Leaf	src/Domain/{BoundedContext}/
Composite	src/Domain/{BoundedContext}/
Unit Tests	tests/Unit/Domain/{BoundedContext}/

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Naming Conventions

Component	Pattern	Example
Component Interface	{Name}Interface	MenuItemInterface
Leaf	{Name}	MenuItem
Composite	{Name}Composite	MenuComposite
Test	{ClassName}Test	MenuCompositeTest

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Quick Template Reference

Component Interface

interface {Name}Interface
{
    public function {operation}(): {returnType};
}

Leaf

final readonly class {Name} implements {Name}Interface
{
    public function {operation}(): {returnType}
    {
        return {leafBehavior};
    }
}

Composite

final class {Name}Composite implements {Name}Interface
{
    private array $children = [];

    public function add({Name}Interface $child): void
    {
        $this->children[] = $child;
    }

    public function {operation}(): {returnType}
    {
        $result = {initialValue};

        foreach ($this->children as $child) {
            $result {combineOperation} $child->{operation}();
        }

        return $result;
    }
}

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Usage Example

$menu = new MenuComposite('Products');
$menu->add(new MenuItem('Laptops'));

$submenu = new MenuComposite('Accessories');
$submenu->add(new MenuItem('Mouse'));
$submenu->add(new MenuItem('Keyboard'));

$menu->add($submenu);

// Uniform treatment
$menu->render();

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Common Composites

Composite	Purpose
MenuComposite	Nested menu structures
PermissionComposite	Permission hierarchies
PriceRuleComposite	Combined pricing rules
FileSystemComposite	Files and directories
OrganizationComposite	Company structure

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Anti-patterns to Avoid

Anti-pattern	Problem	Solution
Type Checking	instanceof checks everywhere	Use polymorphism
Leaf Operations in Composite	add/remove on leafs	Throw exception or use separate interfaces
Deep Hierarchies	Performance issues	Limit depth or use flyweight
Missing Parent Reference	Can't navigate up	Store parent in composite
Circular References	Infinite loops	Validate before adding

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References

For complete PHP templates and examples, see:

• references/templates.md — Component interface, leaf, composite templates
• references/examples.md — Menu, permission, price rule composites with unit tests