services-behaviors.md

Behaviors

• Introduction
• Comparison to traits
• Extending constructors
• Usage example

Introduction

Behaviors add the ability for classes to have private traits, also known as Behaviors. These are similar to native PHP Traits except they have some distinct benefits:

1. Behaviors have their own contructor.
2. Behaviors can have private or protected methods.
3. Methods and property names can conflict safely.
4. Classes can be extended with behaviors dynamically.

Comparison to traits

Where you might use a PHP trait like this:

class MyClass
{
    use \October\Rain\UtilityFunctions;
    use \October\Rain\DeferredBinding;
}

A behavior is used in a similar fashion:

class MyClass extends \October\Rain\Extension\Extendable
{
    public $implement = [
        'October.Rain.UtilityFunctions',
        'October.Rain.DeferredBinding',
    ];
}

Where you might define a trait like this:

trait UtilityFunctions
{
    public function sayHello()
    {
        echo "Hello from " . get_class($this);
    }
}

A behavior is defined like this:

class UtilityFunctions extends \October\Rain\Extension\ExtensionBase
{
    protected $parent;

    public function __construct($parent)
    {
        $this->parent = $parent;
    }

    public function sayHello()
    {
        echo "Hello from " . get_class($this->parent);
    }
}

The extended object is always passed as the first parameter to the Behavior's constructor.

Extending constructors

Any class that uses the Extendable or ExtendableTrait can have its constructor extended with the static extend() method. The argument should pass a closure that will be called as part of the class constructor.

MyNamespace\Controller::extend(function($controller) {
    //
});

Dynamically implementing a behavior

This unique ability to extend constructors allows behaviors to be implemented dynamically, for example:

/**
 * Extend the Pizza Shop to include the Master Splinter behavior too
 */
MyNamespace\Controller::extend(function($controller) {

    // Implement the list controller behavior dynamically
    $controller->implement[] = 'MyNamespace.Behaviors.ListController';
});

Dynamically creating methods

Methods can be created to a extendable object by calling addDynamicMethod and passing a method name and callable object, like a Closure.

Post::extend(function($model) {
    $model->addDynamicMethod('getTagsAttribute', function() use ($model) {
        return $model->tags()->lists('name');
    });
});

Usage example

Behavior / Extension class

<?php namespace MyNamespace\Behaviors;

class FormController extends \October\Rain\Extension\ExtensionBase
{
    /**
     * @var Reference to the extended object.
     */
    protected $controller;

    /**
     * Constructor
     */
    public function __construct($controller)
    {
        $this->controller = $controller;
    }

    public function someMethod()
    {
        return "I come from the FormController Behavior!";
    }

    public function otherMethod()
    {
        return "You might not see me...";
    }
}

Extending a class

This Controller class will implement the FormController behavior and then the methods will become available (mixed in) to the class. We will override the otherMethod method.

<?php namespace MyNamespace;

class Controller extends \October\Rain\Extension\Extendable
{

    /**
     * Implement the FormController behavior
     */
    public $implement = [
        'MyNamespace.Behaviors.FormController'
    ];

    public function otherMethod()
    {
        return "I come from the main Controller!";
    }
}

Using the extension

$controller = new MyNamespace\Controller;

// Prints: I come from the FormController Behavior!
echo $controller->someMethod();

// Prints: I come from the main Controller!
echo $controller->otherMethod();

// Prints: You might not see me...
echo $controller->asExtension('FormController')->otherMethod();

Soft definition

If a behavior class does not exist, like a trait, a Class not found error will be thrown. In some cases you may wish to suppress this error, for conditional implementation if a behavior is present in the system. You can do this by placing an @ symbol at the beginning of the class name.

class User extends \October\Rain\Extension\Extendable
{
    public $implement = ['@RainLab.Translate.Behaviors.TranslatableModel'];
}

If the class name RainLab\Translate\Behaviors\TranslatableModel does not exist, no error will be thrown. This is the equivalent of the following code:

class User extends \October\Rain\Extension\Extendable
{
    public $implement = [];

    public function __construct()
    {
        if (class_exists('RainLab\Translate\Behaviors\TranslatableModel')) {
            $this->implement[] = 'RainLab.Translate.Behaviors.TranslatableModel';
        }

        parent::__construct();
    }
}

Using Traits instead of base classes

In some cases you may not wish to extend the ExtensionBase or Extendable classes, due to other needs. So you can use the traits instead, although obviously the behavior methods will not be available to the parent class.

• When using the ExtensionTrait the methods from ExtensionBase should be applied to the class.

• When using the ExtendableTrait the methods from Extendable should be applied to the class.