Merge pull request #19 from stakisko/master

Data Mapper Pattern Implementation

DataMapper/Test.php

@@ -0,0 +1,27 @@
+<?php 
+
+namespace DesignPatterns;
+
+/**
+ * DataMapper pattern
+ *
+ * Testing the DataMapper Pattern
+ */
+
+	$userMapper = new UserMapper();
+
+	/* fetch a record from Database */
+	$user = $userMapper->findById(1);
+
+	if ($user !== null) {
+		echo "Hello " . $user->getUsername() . ". Your email is " . $user->getEmail();
+	}
+
+	/* save a new record on Database */
+	var $newUser = new User('', 'Odysseus', 'Odysseus@ithaca.gr');
+	$userMapper->save($newUser);
+
+	/* fetch all from a table on Database */
+	var $usersArray = $userMapper->findAll();
+
+?>

DataMapper/User.php

@@ -0,0 +1,48 @@
+<?php
+
+namespace DesignPatterns;
+
+/**
+ * DataMapper pattern
+ *
+ * This is our representation of a DataBase record in the memory
+ *
+ */
+class User
+{
+	protected $userId;
+    protected $username;
+    protected $email;
+
+	public function __construct($id, $username, $email)
+    {
+        $this->id = $id;
+        $this->username = $username;
+        $this->email = $email;
+    }
+
+	public function getUserId() {
+		return $this->userId;
+	}
+
+	public function setUserID($userId) {
+		$this->userId = $userId;
+	}
+
+	public function getUsername() {
+		return $this->username;
+	}
+
+	public function setUsername($username) {
+		$this->username = $username;
+	}
+
+	public function getEmail() {
+		return $this->email;
+	}
+
+	public function setEmail($email) {
+		$this->email = $email;
+	}
+
+}

DataMapper/UserMapper.php

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+<?php
+
+namespace DesignPatterns;
+
+/**
+ * DataMapper pattern
+ *
+ * Purpose:
+ * A Data Mapper, is a Data Access Layer that performs bidirectional transfer of
+ * data between a persistent data store (often a relational database) and an in
+ * memory data representation (the domain layer). The goal of the pattern is to
+ * keep the in memory representation and the persistent data store independent of
+ * each other and the data mapper itself. The layer is composed of one or more
+ * mappers (or Data Access Objects), performing the data transfer. Mapper
+ * implementations vary in scope. Generic mappers will handle many different domain
+ * entity types, dedicated mappers will handle one or a few.
+ * (FROM http://en.wikipedia.org/wiki/Data_mapper_pattern)
+ *
+ *
+ * Examples:
+ * - DB Object Relational Mapper (ORM)
+ *
+ */
+class UserMapper
+{
+
+    protected $_adapter;
+
+    public function __construct(array $options = null)
+    {
+        /**
+         * create new Database connector on $_adapter using specific table
+         *
+         * $_adapter var could be a specific to a table class or a generic 
+         * interface for connecting to Database and do certain jobs
+         */
+    }
+
+    /**
+     * saves a user object from memory to Database
+     *
+     * @return boolean
+     */
+    public function save(User $user)
+    {
+        /* $data keys shoulds correspond to valid Table columns on the Database */
+        $data = array(
+            'userid'   => $user->getUserId(),
+            'username' => $user->getUsername(),
+            'email'   => $user->getEmail(),
+        );
+
+        /* if no ID specified create new user else update the one in the Database */
+        if (null === ($id = $user->getUserId())) {
+            unset($data['userid']);
+            $this->_adapter->insert($data);
+            return true;
+        } else {
+            $this->_adapter->update($data, array('userid = ?' => $id));
+            return true;
+        }
+
+        return false;
+    }
+
+    /**
+     * finds a user from Database based on ID and returns a User object located
+     * in memory
+     *
+     * @return User
+     */
+    public function findById($id)
+    {
+        $result = $this->_adapter->find($id);
+        if (0 == count($result)) {
+            return;
+        }
+        $row = $result->current();
+
+        var user = new User();
+        $user->setUserID($row['userid']);
+        $user->setUsername($row['username']);
+        $user->setEmail($row['email']);
+
+        return user;
+    }
+
+    /**
+     * fetches an array from Database and returns an array of User objects
+     * located in memory
+     *
+     * @return array
+     */
+    public function findAll()
+    {
+        $resultSet = $this->_adapter->findAll();
+        $entries   = array();
+
+        foreach ($resultSet as $row) {
+
+            $entry = new User();
+            $user->setUserID($row['userid']);
+            $user->setUsername($row['username']);
+            $user->setEmail($row['email']);
+
+            $entries[] = $entry;
+        }
+
+        return $entries;
+    }
+}