Chainable class container

README.md

Simple Chain of Responsibility in PHP

Container and Interface for implementing Chain of Responsibility. Allows for variable dependencies per class without hooking into a wider Service Container.

Example

Classes to Chain

<?php

class ResolveNumberOne implements ChainableClass
{
	/**
	 * @var int
	 */
	protected $number;
	
	public function __construct($number)
	{
		$this->number = $number;
	}
	
	public function handle()
	{
		return $this->number === 1 ? 'One' : null;
	}
}

class ResolveNumberTwo implements ChainableClass
{
	/**
	 * @var int
	 */
	protected $number;
	
	public function __construct($number)
	{
		$this->number = $number;
	}
	
	public function handle()
	{
		return $this->number === 2 ? 'Two' : null;
	}
}

Implementation

<?php

$number = 2;

// Returns "Two";
$resolved = (new ChainableClassContainer)
                ->chain(ResolveNumberOne::class, [ $number ])
                ->chain(ResolveNumberTwo::class, [ $number ])
                ->handle();
                
$number = 4;

// Returns null;
$resolved = (new ChainableClassContainer)
                ->chain(ResolveNumberOne::class, [ $number ])
                ->chain(ResolveNumberTwo::class, [ $number ])
                ->handle();

ChainableClass.php

<?php

/**
 * Interface for classes which can be used in a ChainableClassContainer
 */
interface ChainableClass
{
	public function handle();
}

ChainableClassContainer.php

<?php

/**
 * Simple class providing the functionality to chain classes
 */
class ChainableClassContainer
{
	/**
	 * List of classes and their arguments with which to instantiate them
	 *
	 * @var array
	 */
	protected $chain = [];
	
	/**
	 * @param  mixed $class
	 * @param  array $arguments
	 * @return $this
	 */
	public function chain($class, array $arguments = [])
	{
		$this->chain[] = [
			$class,
			$arguments
		];
		
		return $this;
	}
	
	/**
	 * Traverse the list of chainable classes, instantiating, and moving on
	 * if their handle method returns null
	 *
	 * @return mixed|null
	 * @throws \Exception When Class in chain doesn't implement ChainableClass interface
	 */
	public function handle()
	{
		$processed = null;
		foreach($this->chain as $handler)
		{
			$processed = (new $handler[0](...$handler[1]))->handle();
			
			if($processed !== null)
				break;
		}
		
		return $processed;
	}
}