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<?php |
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/** |
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* AppserverIo\Messaging\ArrayMessage |
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* |
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* NOTICE OF LICENSE |
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* |
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* This source file is subject to the Open Software License (OSL 3.0) |
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* that is available through the world-wide-web at this URL: |
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* http://opensource.org/licenses/osl-3.0.php |
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* |
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* PHP version 5 |
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* |
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* @author Tim Wagner <[email protected]> |
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* @copyright 2015 TechDivision GmbH <[email protected]> |
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* @license http://opensource.org/licenses/osl-3.0.php Open Software License (OSL 3.0) |
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* @link https://github.com/appserver-io/messaging |
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* @link http://www.appserver.io |
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*/ |
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namespace AppserverIo\Messaging; |
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use Rhumsaa\Uuid\Uuid; |
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/** |
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* The implementation for sending a message containing |
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* data encapsulated in an array. |
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* |
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* @author Tim Wagner <[email protected]> |
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* @copyright 2015 TechDivision GmbH <[email protected]> |
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* @license http://opensource.org/licenses/osl-3.0.php Open Software License (OSL 3.0) |
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* @link https://github.com/appserver-io/messaging |
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* @link http://www.appserver.io |
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*/ |
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class ArrayMessage extends AbstractMessage |
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{ |
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/** |
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* The message id as hash value. |
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* |
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* @var string |
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*/ |
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protected $messageId = null; |
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/** |
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* The message itself. |
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* |
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* @var array |
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*/ |
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protected $message = null; |
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/** |
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* Initializes the message with the array |
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* to send to the queue. |
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* |
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* @param array $message The array with the data to send |
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*/ |
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public function __construct(array $message) |
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{ |
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// call parent constructor |
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parent::__construct(); |
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// initialize the HashMap sent with the message |
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$this->message = $message; |
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// initialize the message id |
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$this->messageId = Uuid::uuid4()->__toString(); |
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} |
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/** |
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* Returns the unique message-ID. |
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* |
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* @return string The unique message-ID |
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*/ |
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public function getMessageId() |
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{ |
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return $this->messageId; |
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} |
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/** |
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* The message itself. |
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* |
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* @return array The message itself |
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*/ |
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public function getMessage() |
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{ |
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return $this->message; |
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} |
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/** |
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* Returns the message as string. |
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* |
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* @return string The message as string |
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*/ |
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public function __toString() |
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{ |
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return serialize($this->message); |
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} |
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} |
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If you return a value from a function or method, it should be a sub-type of the type that is given by the parent type f.e. an interface, or abstract method. This is more formally defined by the Lizkov substitution principle, and guarantees that classes that depend on the parent type can use any instance of a child type interchangably. This principle also belongs to the SOLID principles for object oriented design.
Let’s take a look at an example:
Our function
my_function
expects aPost
object, and outputs the author of the post. The base classPost
returns a simple string and outputting a simple string will work just fine. However, the child classBlogPost
which is a sub-type ofPost
instead decided to return anobject
, and is therefore violating the SOLID principles. If aBlogPost
were passed tomy_function
, PHP would not complain, but ultimately fail when executing thestrtoupper
call in its body.