rfc:instance_counter

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rfc:instance_counter [2013/04/08 15:56] – [Proposal] frankrfc:instance_counter [2013/05/08 07:28] – [PHP RFC: instance counter] Declined frank
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 ====== PHP RFC: instance counter ====== ====== PHP RFC: instance counter ======
  
-  * Version: 0.1+  * Version: 0.4
   * Date: 2013-04-08   * Date: 2013-04-08
   * Author: Frank Liepert, contact@frank-liepert.de   * Author: Frank Liepert, contact@frank-liepert.de
   * Contributor: Joe Watkins   * Contributor: Joe Watkins
-  * Status: Draft+  * Status: Declined
   * First Published at: http://wiki.php.net/rfc/instance_counter   * First Published at: http://wiki.php.net/rfc/instance_counter
  
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 Coming to Object-Orientated Programming, PHP offers a variety of possibilities to obtain information about classes and their instances (objects). In this regard, the classes/objects functions (http://www.php.net/manual/en/ref.classobj.php) as well as the reflection API (http://www.php.net/manual/en/book.reflection.php) do a great job. But still there is no function to obtain a particular information: the number of instances of a class.  Coming to Object-Orientated Programming, PHP offers a variety of possibilities to obtain information about classes and their instances (objects). In this regard, the classes/objects functions (http://www.php.net/manual/en/ref.classobj.php) as well as the reflection API (http://www.php.net/manual/en/book.reflection.php) do a great job. But still there is no function to obtain a particular information: the number of instances of a class. 
  
-One might say, simply implement a static counter in each class. But what about built-in classes like SPL? A wrapper would be required. Implementing it these ways, it does not only sound, but it actually is cumbersome. The purpose of this RFC is to address this issue.+One might say, simply implement a static counter in each class. But what about built-in classes like SPL? A wrapper would be required. Implementing it these ways, it not only sounds, but actually is cumbersome. The purpose of this RFC is to address this issue.
  
 ===== Proposal ===== ===== Proposal =====
  
-The proposal is to add a new function returning an array ('name of the class' => number of instances) in the current script.+The proposal is to add a new functionality dealing with the number of instances of either a specific class name/object or set of class names/objects or all classes.
  
-The function name should fit in with the current names of class/object functions. Therefore, the name **get_objects_count()** seems to be reasonable, but is still up for discussion (see [[#Function name]]).+The function name should fit in with the current names of class/object functions. Therefore, the name **get_objects_count()** seems to be reasonable.
  
-Example #1:+  * **If no argument is provided, the number of all objects in the object store as an associative array ('class name' => count) will be returned.**
 <code php> <code php>
 print_r (get_objects_count()); print_r (get_objects_count());
 // Array () // Array ()
  
-$foo = new StdClass;+$foo = new stdClass;
  
 print_r (get_objects_count()); print_r (get_objects_count());
-// Array ( [StdClass] => 1 )+// Array ( [stdClass] => 1 )
  
-$bar = new StdClass;+$bar = new stdClass;
  
 print_r (get_objects_count()); print_r (get_objects_count());
-// Array ( [StdClass] => 2 )+// Array ( [stdClass] => 2 )
  
 $bar = null; $bar = null;
  
 print_r (get_objects_count()); print_r (get_objects_count());
-// Array ( [StdClass] => 1 )+// Array ( [stdClass] => 1 )
  
 $foo = null; $foo = null;
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 </code> </code>
  
-==== Use cases: ====+  * **If a class name is provided, the number of objects of the specified class in the object store will be returned.** 
 +<code php> 
 +print get_objects_count('stdClass'); 
 +// 0 
 + 
 +$foo = new stdClass; 
 + 
 +print get_objects_count('stdClass'); 
 +// 1 
 + 
 +$bar = new stdClass; 
 + 
 +print get_objects_count('stdClass'); 
 +// 2 
 + 
 +$bar = null; 
 + 
 +print get_objects_count('stdClass'); 
 +// 1 
 + 
 +$foo = null; 
 + 
 +print get_objects_count('stdClass'); 
 +// 0 
 +</code> 
 + 
 +  * **If an object is provided, the number of objects of the specifiied objects class in the object store will be returned. The return value is always ≥ 1.** 
 +<code php> 
 +$foo = new stdClass; 
 + 
 +print get_objects_count($foo); 
 +// 1 
 + 
 +$bar = new stdClass; 
 + 
 +print get_objects_count($bar); 
 +// 2 
 + 
 +$bar = null; 
 + 
 +print get_objects_count($foo); 
 +// 1 
 +</code> 
 + 
 +  * **If an an array is provided, it will be the treated as an inclusive indexed array of class names. An associative array ('class name' => count) will be returned.** 
 +<code php> 
 +print_r (get_objects_count(array('stdClass'))); 
 +// Array ( [stdClass] => 0 ) 
 + 
 +$foo = new stdClass; 
 + 
 +print_r (get_objects_count(array('stdClass'))); 
 +// Array ( [stdClass] => 1 ) 
 + 
 +$bar = new stdClass; 
 + 
 +print_r (get_objects_count(array('stdClass'))); 
 +// Array ( [stdClass] => 2 ) 
 + 
 +$bar = null; 
 + 
 +print_r (get_objects_count(array('stdClass'))); 
 +// Array ( [stdClass] => 1 ) 
 + 
 +$foo = null; 
 + 
 +print_r (get_objects_count(array('stdClass'))); 
 +// Array ( [stdClass] => 0 ) 
 +</code> 
 + 
 +===== General questions & answers ===== 
 + 
 +==== Inheritance ==== 
 + 
 +On internals list there was the question, if only the "direct" instances of a class or also the instances of subclasses are counted? The answer is: only direct instances. See the following code: 
 +<code php> 
 +class A {} 
 +class B extends A {} 
 + 
 +print get_objects_count('A'); 
 +// 0 
 + 
 +$b = new B; 
 + 
 +var_dump($b instanceof A); 
 +// bool(true) 
 + 
 +print get_objects_count('A'); 
 +// 0 
 + 
 +print get_objects_count('B'); 
 +// 1 
 +</code> 
 + 
 +===== Use cases: =====
   * Debugging   * Debugging
   * Implementation of design patterns (f.ex. flyweight pattern)   * Implementation of design patterns (f.ex. flyweight pattern)
   * Extended control: limit the number of objects   * Extended control: limit the number of objects
 +  * Teach people about assignment of objects
   * to be continued...   * to be continued...
  
 ===== Function name ===== ===== Function name =====
  
-Further suggestions for the function name in example #1:+Since there were no objections against the proposed function name, its status changes to accepted.
 <code> <code>
-// Proposed+// Proposed + Accepted
 get_objects_count() get_objects_count()
  
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 ===== Open Issues ===== ===== Open Issues =====
  
-  * Decision on function name. +None.
-  * <del>Decision on whether it should be in Reflection.</del> +
 ===== Patches and Tests ===== ===== Patches and Tests =====
  
-A first implementation: https://gist.github.com/krakjoe/5275773+Implementation: https://gist.github.com/krakjoe/5275773
  
 Tests need to be done. Tests need to be done.
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 - None. - None.
 +
 +===== Vote =====
 +<doodle title="Should this RFC be implemented?" auth="frank" voteType="single" closed="true">
 +   * Yes
 +   * No
 +</doodle>
 +    
 +==== Voting period ====
 +Start: **2013/04/30**
 +
 +End: **2013/05/07**
rfc/instance_counter.txt · Last modified: 2017/09/22 13:28 by 127.0.0.1