Add an easy way to set callback priorities for behaviors

Behaviors often use priorities, make it easy to define the priority
of callbacks a behavior provides when binding it to a table.

Cake/ORM/Behavior.php

@@ -67,6 +67,10 @@
  * event fired from your Table classes including custom application
  * specific ones.
  *
+ * You can set the priority of a behaviors callbacks by using the
+ * `priority` setting when attaching a behavior. This will set the
+ * priority for all the callbacks a behavior provides.
+ *
  * ## Finder methods
  *
  * Behaviors can provide finder methods that hook into a Table's
@@ -83,6 +87,7 @@
  *
  *
  * @see Cake\ORM\Table::addBehavior()
+ * @see Cake\Event\EventManager
  */
 class Behavior implements EventListener {
 
@@ -91,7 +96,29 @@ class Behavior implements EventListener {
  *
  * @var array
  */
-	public $settings = [];
+	protected $_settings = [];
+
+/**
+ * Constructor
+ *
+ * Does not retain a reference to the Table object. If you need this
+ * you should override the constructor.
+ *
+ * @param Table $table The table this behavior is attached to.
+ * @param array $settings The settings for this behavior.
+ */
+	public function __construct(Table $table, array $settings = []) {
+		$this->_settings = $settings;
+	}
+
+/**
+ * Read the settings being used.
+ *
+ * @return array
+ */
+	public function settings() {
+		return $this->_settings;
+	}
 
 /**
  * Get the Model callbacks this behavior is interested in.
@@ -112,10 +139,21 @@ public function implementedEvents() {
 			'Model.beforeDelete' => 'beforeDelete',
 			'Model.afterDelete' => 'afterDelete',
 		];
+		$settings = $this->settings();
+		$priority = isset($settings['priority']) ? $settings['priority'] : null;
 		$events = [];
+
 		foreach ($eventMap as $event => $method) {
-			if (method_exists($this, $method)) {
+			if (!method_exists($this, $method)) {
+				continue;
+			}
+			if ($priority === null) {
 				$events[$event] = $method;
+			} else {
+				$events[$event] = [
+					'callable' => $method,
+					'priority' => $priority
+				];
 			}
 		}
 		return $events;

Cake/Test/TestCase/ORM/BehaviorTest.php

@@ -0,0 +1,90 @@
+<?php
+/**
+ * CakePHP(tm) : Rapid Development Framework (http://cakephp.org)
+ * Copyright (c) Cake Software Foundation, Inc. (http://cakefoundation.org)
+ *
+ * Licensed under The MIT License
+ * For full copyright and license information, please see the LICENSE.txt
+ * Redistributions of files must retain the above copyright notice.
+ *
+ * @copyright     Copyright (c) Cake Software Foundation, Inc. (http://cakefoundation.org)
+ * @link          http://cakephp.org CakePHP(tm) Project
+ * @since         CakePHP(tm) v 3.0.0
+ * @license       MIT License (http://www.opensource.org/licenses/mit-license.php)
+ */
+namespace Cake\Test\TestCase\ORM;
+
+use Cake\ORM\Behavior;
+use Cake\TestSuite\TestCase;
+
+/**
+ * Test Stub.
+ */
+class TestBehavior extends Behavior {
+
+/**
+ * Test for event bindings.
+ */
+	public function beforeFind() {
+	}
+
+}
+
+/**
+ * Behavior test case
+ */
+class BehaviorTest extends TestCase {
+
+/**
+ * setup
+ *
+ * @return void
+ */
+	public function setUp() {
+		parent::setUp();
+	}
+
+/**
+ * Test the side effects of the constructor.
+ *
+ * @return void
+ */
+	public function testConstructor() {
+		$table = $this->getMock('Cake\ORM\Table');
+		$settings = ['key' => 'value'];
+		$behavior = new TestBehavior($table, $settings);
+		$this->assertEquals($settings, $behavior->settings());
+	}
+
+/**
+ * Test the default behavior of implementedEvents
+ *
+ * @return void
+ */
+	public function testImplementedEvents() {
+		$table = $this->getMock('Cake\ORM\Table');
+		$behavior = new TestBehavior($table);
+		$expected = [
+			'Model.beforeFind' => 'beforeFind'
+		];
+		$this->assertEquals($expected, $behavior->implementedEvents());
+	}
+
+/**
+ * Test that implementedEvents uses the priority setting.
+ *
+ * @return void
+ */
+	public function testImplementedEventsWithPriority() {
+		$table = $this->getMock('Cake\ORM\Table');
+		$behavior = new TestBehavior($table, ['priority' => 10]);
+		$expected = [
+			'Model.beforeFind' => [
+				'priority' => 10,
+				'callable' => 'beforeFind'
+			]
+		];
+		$this->assertEquals($expected, $behavior->implementedEvents());
+	}
+
+}