Calling static method in PHP 5.3 Late Static Binding Singleton Method
I have an abstract class that contains these methods:
<?php
public static function getInstance() {
$me = get_called_class();
if (!isset(self::$_instances[$me])) {
$ref = new ReflectionClass($me);
self::$_instances[$me] = $reflection_object->newInstance();
self::$_instances[$me]->init();
}
return self::$_instances[$me];
}
public function __construct() {
$me = get_class($this);
if(isset(self::$_instances[$me])) {
throw new Exception('The singleton class has already been instantiated!');
} else {
self::$_instances[$me] = $this;
$this->_className = $me;
}
}
It works exactly as I had expected when instantiating within sibling singletons. I am having an issue when attempting to get an instance from a child class that does not share the same superclass.
My stack trace is:
Fatal error: Call to undefined method Keywords_AdminMenu_OptionsTable::init() in D:\webroot\domains\dev.slbmeh.com\htdocs\wordpress\wp-content\plugins\LocalGiant_WPF\library\LocalGiant\Module\Abstract.php on line 149
Call Stack:
0.0012 331664 1. {main}() D:\webroot\domains\dev.slbmeh.com\htdocs\wordpress\wp-admin\admin.php:0
0.7772 3224864 2. do_action() D:\webroot\domains\dev.slbmeh.com\htdocs\wordpress\wp-admin\admin.php:151
0.7774 3225792 3. call_user_func_array() D:\webroot\domains\dev.slbmeh.com\htdocs\wordpress\wp-includes\plugin.php:405
0.7774 3225808 4. Keywords_AdminMenu->showMenu() D:\webroot\domains\de开发者_开发问答v.slbmeh.com\htdocs\wordpress\wp-includes\plugin.php:405
0.7796 3227016 5. Keywords_AdminMenu_View::showMenu() D:\webroot\domains\dev.slbmeh.com\htdocs\wordpress\wp-content\plugins\LocalGiant_WPF\modules\Keywords\AdminMenu.php:29
0.7821 3240776 6. Keywords_AdminMenu_OptionsTable->prepareItems() D:\webroot\domains\dev.slbmeh.com\htdocs\wordpress\wp-content\plugins\LocalGiant_WPF\modules\Keywords\AdminMenu\View.php:25
0.7822 3241824 7. LocalGiant_Module_Abstract->getInstance() D:\webroot\domains\dev.slbmeh.com\htdocs\wordpress\wp-content\plugins\LocalGiant_WPF\modules\Keywords\AdminMenu\OptionsTable.php:90
The init() method is an abstract method in the Singleton superclass. The class Keywords_AdminMenu_OptionsTable is a subclass of a class from a separate set of libraries, WP_List_Table from WordPress.
A broken down copy of the class Keywords_AdminMenu_Options table is as follows:
<?php
class Keywords_AdminMenu_OptionsTable extends WP_List_Table {
public function __construct(){
global $status, $page;
//Set parent defaults
parent::__construct( array(
'singular' => 'module',
'plural' => 'modules',
'ajax' => false
) );
}
function prepareItems() {
/* SNIP - Prepare my SQL query. */
$moduleDatabase = Database_Module::getInstance();
$current_page = $this->get_pagenum();
$keywords = $moduleDatabase->simpleQuery($sql, $moduleLoader->getMyNamespace());
/* SNIP - Handle my SQL data. */
}
}
The contents of WP_List_Table found here: http://core.trac.wordpress.org/browser/tags/3.2.1//wp-admin/includes/class-wp-list-table.php
It turns out my code did not have getInstance declared static. This snippet of code gives a little more insight to how the static bindings affect the bindings.
<pre><?php
class Singleton_Super {
protected static $_instances = array();
protected $_className;
public function singletonSuperTest() {
$getCalled = get_called_class();
$getClass = get_class($this);
$getName = $this->_className;
echo "\nSingleton_Super::singletonSuperTest()\n";
echo "\tget_called_class() = $getCalled\n";
echo "\tget_class(\$this) = $getClass\n";
echo "\t_className() = $getName\n";
}
public function whatsMyName() {
echo "\nSingleton_Super::whatsMyName()\n\t$this->_className\n";
}
public static function getInstance() {
$me = get_called_class();
echo "\nSingleton_Super::getInstance()\n\tget_called_class() = $me\n";
if (!isset(self::$_instances[$me])) {
$ref = new ReflectionClass($me);
self::$_instances[$me] = $ref->newInstance();
}
return self::$_instances[$me];
}
public function __construct() {
$me = get_class($this);
echo "\nSingleton_Super::__construct()\n\tget_called_class() = $me\n";
if(isset(self::$_instances[$me])) {
throw new Exception("The Singleton class, '$me', has already been instantiated.");
} else {
self::$_instances[$me] = $this;
$this->_className = $me;
}
}
public function __clone() {
trigger_error("Cloning is not allowed.", E_USER_ERROR);
}
public function __wakeup() {
trigger_error("Unserializing is not allowed.", E_USER_ERROR);
}
}
class Singleton_Child extends Singleton_Super {
public function singletonTest() {
$getCalled = get_called_class();
$getClass = get_class($this);
$getName = $this->_className;
echo "\nSingleton_Child::singletonTest()\n";
echo "\tget_called_class() = $getCalled\n";
echo "\tget_class(\$this) = $getClass\n";
echo "\t_className() = $getName\n";
}
}
class Outer_Concrete_Super {
protected $_className;
public function __construct() {
$me = get_class($this);
$this->_className = $me;
echo "\nOuter_Concrete_Super::__construct()\n\tget_class(\$this) = $me\n";
}
public function whatsMyName() {
echo $this->_className;
}
public function concreteSuperTest() {
$getCalled = get_called_class();
$getClass = get_class($this);
$getName = $this->_className;
echo "\nOuter_Concrete_Super::concreteSuperTest()\n";
echo "\tget_called_class() = $getCalled\n";
echo "\tget_class(\$this) = $getClass\n";
echo "\t_className() = $getName\n";
}
public function superUseSingletonChild() {
$singleton = Singleton_Child::getInstance();
$singleton->singletonTest();
}
}
class Outer_Concrete_Child extends Outer_Concrete_Super {
public function concreteTest() {
$getCalled = get_called_class();
$getClass = get_class($this);
$getName = $this->_className;
echo "\nOuter_Concrete_Super::concreteSuperTest()\n";
echo "\tget_called_class() = $getCalled\n";
echo "\tget_class(\$this) = $getClass\n";
echo "\t\$_className = $getName\n";
}
public function bigTest() {
$singleton = Singleton_Child::getInstance();
$singleton->whatsMyName();
$singleton->singletonSuperTest();
$singleton->singletonTest();
}
}
echo "\n*****************************\n";
echo "* Constructors *\n";
echo "*****************************\n\n";
$singleP = Singleton_Super::getInstance();
$singleC = Singleton_Child::getInstance();
$outerP = new Outer_Concrete_Super;
$outerC = new Outer_Concrete_Child;
echo "\n*****************************\n";
echo "* Third Party Class Testing *\n";
echo "*****************************\n\n";
$outerP->concreteSuperTest();
$outerC->concreteSuperTest();
$outerC->concreteTest();
$outerC->bigTest();
echo "\n*****************************\n";
echo "* Singleton *\n";
echo "*****************************\n\n";
$singleP->whatsMyName();
$singleP->singletonSuperTest();
$singleC->whatsMyName();
$singleC->singletonSuperTest();
$singleC->singletonTest();
?>
</pre>
Returns the result:
*****************************
* Constructors *
*****************************
Singleton_Super::getInstance()
get_called_class() = Singleton_Super
Singleton_Super::__construct()
get_called_class() = Singleton_Super
Singleton_Super::getInstance()
get_called_class() = Singleton_Child
Singleton_Super::__construct()
get_called_class() = Singleton_Child
Outer_Concrete_Super::__construct()
get_class($this) = Outer_Concrete_Super
Outer_Concrete_Super::__construct()
get_class($this) = Outer_Concrete_Child
*****************************
* Third Party Class Testing *
*****************************
Outer_Concrete_Super::concreteSuperTest()
get_called_class() = Outer_Concrete_Super
get_class($this) = Outer_Concrete_Super
_className() = Outer_Concrete_Super
Outer_Concrete_Super::concreteSuperTest()
get_called_class() = Outer_Concrete_Child
get_class($this) = Outer_Concrete_Child
_className() = Outer_Concrete_Child
Outer_Concrete_Super::concreteSuperTest()
get_called_class() = Outer_Concrete_Child
get_class($this) = Outer_Concrete_Child
$_className = Outer_Concrete_Child
Singleton_Super::getInstance()
get_called_class() = Singleton_Child
Singleton_Super::whatsMyName()
Singleton_Child
Singleton_Super::singletonSuperTest()
get_called_class() = Singleton_Child
get_class($this) = Singleton_Child
_className() = Singleton_Child
Singleton_Child::singletonTest()
get_called_class() = Singleton_Child
get_class($this) = Singleton_Child
_className() = Singleton_Child
*****************************
* Singleton *
*****************************
Singleton_Super::whatsMyName()
Singleton_Super
Singleton_Super::singletonSuperTest()
get_called_class() = Singleton_Super
get_class($this) = Singleton_Super
_className() = Singleton_Super
Singleton_Super::whatsMyName()
Singleton_Child
Singleton_Super::singletonSuperTest()
get_called_class() = Singleton_Child
get_class($this) = Singleton_Child
_className() = Singleton_Child
Singleton_Child::singletonTest()
get_called_class() = Singleton_Child
get_class($this) = Singleton_Child
_className() = Singleton_Child
Where if you change the binding on getInstance from static you receive a result of:
*****************************
* Constructors *
*****************************
Singleton_Super::getInstance()
get_called_class() = Singleton_Super
Singleton_Super::__construct()
get_called_class() = Singleton_Super
Singleton_Super::getInstance()
get_called_class() = Singleton_Child
Singleton_Super::__construct()
get_called_class() = Singleton_Child
Outer_Concrete_Super::__construct()
get_class($this) = Outer_Concrete_Super
Outer_Concrete_Super::__construct()
get_class($this) = Outer_Concrete_Child
*****************************
* Third Party Class Testing *
*****************************
Outer_Concrete_Super::concreteSuperTest()
get_called_class() = Outer_Concrete_Super
get_class($this) = Outer_Concrete_Super
_className() = Outer_Concrete_Super
Outer_Concrete_Super::concreteSuperTest()
get_called_class() = Outer_Concrete_Child
get_class($this) = Outer_Concrete_Child
_className() = Outer_Concrete_Child
Outer_Concrete_Super::concreteSuperTest()
get_called_class() = Outer_Concrete_Child
get_class($this) = Outer_Concrete_Child
$_className = Outer_Concrete_Child
Singleton_Super::getInstance()
get_called_class() = Outer_Concrete_Child
Outer_Concrete_Super::__construct()
get_class($this) = Outer_Concrete_Child
Outer_Concrete_Child
Fatal error: Call to undefined method Outer_Concrete_Child::singletonSuperTest() in C:\inetpub\vhosts\BetterOffLocal.com\httpdocs\wp-content\plugins\LocalGiant_WPF\Singleton-Test.php on line 128
I hope this answer helps somebody out. Or at least gives insight as to how to go about troubleshooting such a problem.
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