Added alias support

README.md

@@ -26,6 +26,8 @@ Collection of extensions to the doctrine2 ORM
     - UTCTimestampableEntity - [Timestampable](https://github.com/Atlantic18/DoctrineExtensions/blob/master/doc/timestampable.md)
     behaviour using UTCDateTime
     - EntityManagerAwareTrait - Provides getters/setters for object to hold and instance of an EntityManager. 
+  - Alias
+    - A smarter alias to use with the doctrine query builder. Allows building / chaining of multiple aliases for subquries.
 
 
 ## Skipper

src/ORM/Alias.php

@@ -0,0 +1,128 @@
+<?php
+
+namespace DoctrineExtensions\ORM;
+
+/**
+ * Provides an easy way to work with aliases for doctrine entities.
+ *
+ * Allows chaining of aliases to reduce the chance of collisions when
+ * working with subqueries.
+ */
+class Alias
+{
+    /**
+     * Chain of aliases
+     *
+     * @var string|\string[]
+     */
+    protected $stack = [];
+
+    /**
+     * Global counter to allow generation of
+     * unique aliases.
+     *
+     * @var int
+     */
+    protected static $counter=0;
+
+    /**
+     * Constructs a new alias instance.
+     * If passed parameter is an array, it completely replaces
+     * the internal stack.
+     *
+     * @param string|string[] $alias
+     */
+    public function __construct($alias = 'a')
+    {
+        if (is_array($alias)) {
+            $this->stack = $alias;
+            return;
+        }
+
+        $this->stack[] = $alias;
+    }
+
+    /**
+     * Adds another level.
+     * The current alias will be copied
+     * with the specified alias added on
+     *
+     * @param string $next alias to add to the stack
+     * @return Alias
+     */
+    public function add($next)
+    {
+        return new self(array_merge($this->stack, (array)$next));
+    }
+
+    /**
+     * Adds another level of alias.
+     *
+     * This method combines the prefix with a unique
+     * counter to ensure that the alias is unique.
+     *
+     * Use this method with care as it will tend to create
+     * misses in the doctrine query cache.
+     *
+     * @param string $prefix Prefix to use with alias
+     * @return Alias
+     */
+    public function addUnique($prefix)
+    {
+        return $this->add($prefix . (self::$counter++));
+    }
+
+    /**
+     * Writes out a field name
+     *
+     * @param string $name
+     * @return string
+     */
+    public function field($name)
+    {
+        return $this->alias() . '.' . $name;
+    }
+
+    /**
+     * Writes out a parameter name
+     *
+     * @param string $name
+     * @return string
+     */
+    public function param($name)
+    {
+        return $this->alias() . '_' . $name;
+    }
+
+    /**
+     * Returns the string version of the alias.
+     *
+     * @return string
+     */
+    public function alias()
+    {
+        return join('_', $this->stack);
+    }
+
+    public function __toString()
+    {
+        return $this->alias();
+    }
+
+
+    /**
+     * Conditionally creates the alias.
+     * If the passed object is already an alias, simply returns it.
+     *
+     * @param string|Alias $alias
+     * @return Alias
+     */
+    public static function create($alias)
+    {
+        if ($alias instanceof self) {
+            return $alias;
+        }
+
+        return new self($alias);
+    }
+}

tests/DoctrineExtensions/Test/ORM/AliasTest.php

@@ -0,0 +1,55 @@
+<?php
+
+namespace DoctrineExtensions\Test\ORM;
+
+use DoctrineExtensions\ORM\Alias;
+
+class AliasTest extends \PHPUnit_Framework_TestCase
+{
+    public function testField()
+    {
+        $alias = new Alias();
+
+        $this->assertEquals('a.foo', $alias->field('foo'));
+    }
+
+    public function testParam()
+    {
+        $alias = new Alias();
+        $this->assertEquals('a_foo', $alias->param('foo'));
+    }
+
+    public function testAlias()
+    {
+        $alias = new Alias(['foo', 'bar']);
+        $this->assertEquals('foo_bar', $alias->alias());
+    }
+
+    public function testAdd()
+    {
+        $alias = new Alias('a');
+        $alias2 = $alias->add('b');
+        $alias3 = $alias2->add('c');
+
+        $this->assertEquals('a', $alias->alias());
+        $this->assertEquals('a_b', $alias2->alias());
+        $this->assertEquals('a_b_c', $alias3->alias());
+    }
+
+    public function testAddUnique()
+    {
+        $alias = new Alias('a');
+        $alias2 = $alias->addUnique('b');
+        $alias3 = $alias2->addUnique('b');
+        $alias4 = $alias3->addUnique('b');
+
+        $this->assertEquals('a_b0_b1_b2', $alias4->alias());
+        $this->assertEquals('a_b3', $alias->addUnique('b')->alias());
+    }
+
+    public function testToString()
+    {
+        $alias = new Alias(['foo', 'bar']);
+        $this->assertEquals('foo_bar', $alias . '');
+    }
+}