rfc:instance_counter

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rfc:instance_counter [2013/04/08 16:01]
frank [Proposal] typo
rfc:instance_counter [2017/09/22 13:28] (current)
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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());​
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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.1365436896.txt.gz · Last modified: 2017/09/22 13:28 (external edit)