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:
- Behaviors have their own constructor.
- Behaviors can have private or protected methods.
- Methods and property names can conflict safely.
- Classes can be extended with behaviors dynamically.
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 $implement = [
\October\Rain\UtilityFunctions::class,
\October\Rain\DeferredBinding::class,
];
}
Where you might define a trait like this:
trait UtilityFunctions
{
public function sayHello()
{
echo "Hello from " . get_class($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.
To summarize:
- Extend \October\Rain\Extension\ExtensionBase to declare your class as a Behaviour
- The class wanting to implement the Behaviour needs to extend \October\Rain\Extension\Extendable
Note: See Using Traits Instead of Base Classes
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($controller) {
//
});
Properties can be declared on an extendable object by calling addDynamicProperty and passing a property name and value.
Post::extend(function($model) {
$model->addDynamicProperty('tagsCache', null);
});
Note: Attempting to set undeclared properties directly on the object that implements the October\Rain\Extension\ExtendableTrait will throw an expection.
Properties created dynamically can be retrieved with the getDynamicProperties function inherited from the ExtendableTrait.
So retrieving all dynamic properties would look like this:
$model->getDynamicProperties();
This will return an associative array [key => value], with the key being the dynamic property name and the value being the property value.
If we know what property we want we can simply append the key (property name) to the function:
$model->getDynamicProperties()[$key];
Methods can be created to an extendable object by calling addDynamicMethod and passing a method name and callable object, like a Closure.
Post::extend(function($model) {
$model->addDynamicProperty('tagsCache', null);
$model->addDynamicMethod('getTagsAttribute', function() use ($model) {
if ($this->tagsCache) {
return $this->tagsCache;
} else {
return $this->tagsCache = $model->tags()->lists('name');
}
});
});
You can check for the existence of a method in an Extendable class by using the methodExists method - similar to the PHP method_exists() function. This will detect both standard methods and dynamic methods that have been added through a addDynamicMethod call. methodExists accepts one parameter: a string of the method name to check the existence of.
Post::extend(function($model) {
$model->addDynamicMethod('getTagsAttribute', function () use ($model) {
return $this->tagsCache;
});
});
$post = new Post;
$post->methodExists('getTagsAttribute'); // true
$post->methodExists('missingMethod'); // false
To retrieve a list of all available methods in an Extendable class, you can use the getClassMethods method. This method operates similar to the PHP get_class_methods() function in that it returns an array of available methods in a class, but in addition to defined methods in the class, it will also list any methods provided by an extension or through an addDynamicMethod call.
Post::extend(function($model) {
$model->addDynamicMethod('getTagsAttribute', function () use ($model) {
return $this->tagsCache;
});
});
$post = new Post;
$methods = $post->getClassMethods();
/**
* $methods = [
* 0 => '__construct',
* 1 => 'extend',
* 2 => 'getTagsAttribute',
* ...
* ];
*/
This unique ability to extend constructors allows behaviors to be implemented dynamically, for example:
/**
* Extend the RainLab.Users controller to include the RelationController behavior too
*/
RainLab\Users\Controllers\Users::extend(function($controller) {
// Implement the list controller behavior dynamically
$controller->implement[] = 'Backend.Behaviors.RelationController';
// Declare the relationConfig property dynamically for the RelationController behavior to use
$controller->addDynamicProperty('relationConfig', '$/myvendor/myplugin/controllers/users/config_relation.yaml');
});
<?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...";
}
}
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!";
}
}
$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();
To check if an object has been extended with a behavior, you may use the isClassExtendedWith method on the object.
$controller->isClassExtendedWith('Backend.Behaviors.RelationController');
Below is an example of dynamically extending a UsersController of a third-party plugin utilizing this method to avoid preventing other plugins from also extending the afore-mentioned third-party plugin.
UsersController::extend(function($controller) {
// Implement behavior if not already implemented
if (!$controller->isClassExtendedWith('Backend.Behaviors.RelationController')) {
$controller->implement[] = 'Backend.Behaviors.RelationController';
}
// Define property if not already defined
if (!isset($controller->relationConfig)) {
$controller->addDynamicProperty('relationConfig');
}
// Splice in configuration safely
$myConfigPath = '$/myvendor/myplugin/controllers/users/config_relation.yaml';
$controller->relationConfig = $controller->mergeConfig(
$controller->relationConfig,
$myConfigPath
);
}
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::class
];
}
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::class;
}
parent::__construct();
}
}
Sometimes your class may already extend a parent class outside of your source control, making it so you are unable to extend the ExtensionBase or Extendable classes. Instead you can use these traits and your classes will have to be implemented as follows.
First let's create the class that will act as a Behaviour, ie. can be implemented by other classes.
<?php namespace MyNamespace\Behaviors;
class WaveBehaviour
{
use \October\Rain\Extension\ExtensionTrait;
/**
* When using the Extensiontrait, your behaviour also has to implement this method
* @see \October\Rain\Extension\ExtensionBase
*/
public static function extend(callable $callback)
{
self::extensionExtendCallback($callback);
}
public function wave()
{
echo "*waves*<br>";
}
}
Now let's create the class that is able to implement behaviours using the ExtendableTrait.
class AI
{
use \October\Rain\Extension\ExtendableTrait;
/**
* @var array Extensions implemented by this class.
*/
public $implement;
/**
* Constructor
*/
public function __construct()
{
$this->extendableConstruct();
}
public function __get($name)
{
return $this->extendableGet($name);
}
public function __set($name, $value)
{
$this->extendableSet($name, $value);
}
public function __call($name, $params)
{
return $this->extendableCall($name, $params);
}
public static function __callStatic($name, $params)
{
return self::extendableCallStatic($name, $params);
}
public static function extend(callable $callback)
{
self::extendableExtendCallback($callback);
}
public function youGotBrains()
{
echo "I've got an AI!<br>";
}
}
The AI class is now able to use behaviours. Let's extend it and have this class implement the WaveBehaviour.
<?php namespace MyNamespace\Classes;
class Robot extends AI
{
public $implement = [
\MyNamespace\Behaviors\WaveBehaviour::class
];
public function identify()
{
echo "I'm a Robot<br>";
echo $this->youGotBrains();
echo $this->wave();
}
}
You can now utilize the Robot as follows:
$robot = new Robot();
$robot->identify();
Which will output:
I'm a Robot
I've got an AI!
*waves*
Remember:
- When using the
ExtensionTraitthe methods fromExtensionBaseshould be applied to the class. - When using the
ExtendableTraitthe methods fromExtendableshould be applied to the class.