rfc:static_constructor

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rfc:static_constructor [2024/06/18 21:45] – erickcomprfc:static_constructor [2024/06/19 12:22] (current) – Clarifying exception handling erickcomp
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   * Date: 2024-06-08   * Date: 2024-06-08
   * Author: Erick de Azevedo Lima <ericklima.comp@gmail.com>   * Author: Erick de Azevedo Lima <ericklima.comp@gmail.com>
-  * Status: Draft+  * Status: Under Discussion 
   * Target Version: PHP 8.4   * Target Version: PHP 8.4
-  * Implementation: <https://github.com/erickcomp/php-src_static-constructor/tree/master>+  * Implementation: https://github.com/php/php-src/compare/master...erickcomp:php-src_static-constructor:master
   * First Published at: https://wiki.php.net/rfc/static_constructor   * First Published at: https://wiki.php.net/rfc/static_constructor
  
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         // could get it from config, database or whatever          // could get it from config, database or whatever 
         self::$minDate = new \DatetimeImmutable('2024-01-01 00:00:00');         self::$minDate = new \DatetimeImmutable('2024-01-01 00:00:00');
-         
     }     }
          
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 } }
  
- 
-$c = new MyClass(scheduledDate: new \DateTimeImmutable('2024-01-01 00:00:00')); 
- 
-var_dump($c); 
 </PHP> </PHP>
  
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         // could get it from config, database or whatever          // could get it from config, database or whatever 
         self::$minDate = new \DatetimeImmutable('2024-01-01 00:00:00');         self::$minDate = new \DatetimeImmutable('2024-01-01 00:00:00');
-         
     }     }
          
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 // Boom! getMinDate does not check if MyClass::$minDate was initialized // Boom! getMinDate does not check if MyClass::$minDate was initialized
 echo MyClass::getMinDate()->format('d/m/Y H:i:s') . PHP_EOL; echo MyClass::getMinDate()->format('d/m/Y H:i:s') . PHP_EOL;
- 
-$c = new MyClass(scheduledDate: new \DateTimeImmutable('2024-01-01 00:00:00')); 
  
 var_dump($c); var_dump($c);
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 ===== Previous RFC on this subject ===== ===== Previous RFC on this subject =====
  
-There was a previous attempt to create an RFC for static constructors, which can be found at: +There was a previous attempt to create an RFC for static constructors, which can be found at: https://externals.io/message/84602
-<https://externals.io/message/84602>+
  
  
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 This RFC does not intend to promote the indiscriminate usage of static properties but rather to provide a way to properly initialize them when they are useful. This RFC does not intend to promote the indiscriminate usage of static properties but rather to provide a way to properly initialize them when they are useful.
  
-==== Implementation on other programming languages ====+===== Implementation on other programming languages =====
  
-=== Java ===+==== Java ====
  
 Java does not have a so-called static constructor, but it provides other ways to initialize static properties: Java does not have a so-called static constructor, but it provides other ways to initialize static properties:
  
-== 1 - <code>static</code> blocks: ==+=== 1 - static blocks: ===
  
-<code>java+<code java>
 import java.util.*; import java.util.*;
 import java.lang.*; import java.lang.*;
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 } }
 </code> </code>
-== 2 - Initialization using method calls: ==+=== 2 - Initialization using method calls: ===
  
-<code>java+<code java>
 import java.util.*; import java.util.*;
 import java.lang.*; import java.lang.*;
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 } }
 </code> </code>
 +https://docs.oracle.com/javase/tutorial/java/javaOO/initial.html
  
-<https://docs.oracle.com/javase/tutorial/java/javaOO/initial.html> +==== Kotlin ====
- +
-=== Kotlin ===+
 Kotlin, strictly speaking, does not offer static members/methods. However, they can be implemented using companion objects and the <php>@JvmStatic</php> annotation: Kotlin, strictly speaking, does not offer static members/methods. However, they can be implemented using companion objects and the <php>@JvmStatic</php> annotation:
  
-<code>kotlin+<code kotlin>
 class Whatever { class Whatever {
     companion object {     companion object {
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 </code> </code>
  
-<https://kotlinlang.org/docs/object-declarations.html#companion-objects>+https://kotlinlang.org/docs/object-declarations.html#companion-objects
  
-=== C\# ===+==== C# ====
  
 C# implements a mechanism called "static constructor". It's a method with no modifiers and has even more restrictions than the private access modifier. It can only be called by the CLR (Common Language Runtime), which gives guarantees about its execution: C# implements a mechanism called "static constructor". It's a method with no modifiers and has even more restrictions than the private access modifier. It can only be called by the CLR (Common Language Runtime), which gives guarantees about its execution:
  
  
-= 1 - Static constructor is called at most one time by the CLR; = +  - Static constructor is called at most one time by the CLR; 
-= 2 - Static constructor is called before any instance constructor is invoked or member is accessed; =+  - Static constructor is called before any instance constructor is invoked or member is accessed;
  
-<code>csharp+<code csharp>
 using System; using System;
 using System.Reflection; using System.Reflection;
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 public class C1 public class C1
 { {
- public static int myVar; +    public static int myVar; 
-  +     
- static C1() +    static C1() 
- { +    { 
- C1.initStaticProps(); +        C1.initStaticProps(); 
- Console.WriteLine("C1::__staticConstructor"); +        Console.WriteLine("C1::__staticConstructor"); 
- } +    } 
-  +     
- public static void initStaticProps() +    public static void initStaticProps() 
- { +    { 
- C1.myVar = 10; +        C1.myVar = 10; 
- Console.WriteLine("Initializing C1::test"); +        Console.WriteLine("Initializing C1::test"); 
-  +    } 
- } +     
-  +    public static void test() 
- public static void test() +    { 
- { +        Console.WriteLine("C1::test"); 
- Console.WriteLine("C1::test"); +    }
- }+
 } }
  
 public class Program public class Program
 { {
- public static void Main() +    public static void Main() 
- { +    { 
- /// Any reference to the C1 class will trigger the static constructor: ///+        /// Any reference to the C1 class will trigger the static constructor: ///
                  
- // Reflection +        // Reflection 
- //Type c1Type = typeof(C1); +        //Type c1Type = typeof(C1); 
-  +         
- // Instance constructor +        // Instance constructor 
- //var c = new C1(); +        //var c = new C1(); 
-  +         
- // Static method call +        // Static method call 
- //C1.test(); +        //C1.test(); 
-  +         
- // Property access +        // Property access 
- Console.WriteLine("C1::myVar:" + C1.myVar); +        Console.WriteLine("C1::myVar:" + C1.myVar); 
- }+    }
 } }
 </code> </code>
  
-<https://learn.microsoft.com/en-us/dotnet/csharp/programming-guide/classes-and-structs/static-constructors> +https://learn.microsoft.com/en-us/dotnet/csharp/programming-guide/classes-and-structs/static-constructors
  
-=== C++ ===+==== C++ ====
 Since its 2017 specification "C++17", C++ provides a way to declare constant expression lambdas (equivalent to PHP's closures). This allows leveraging this feature to initialize complex values for static properties using an <php>inline</php> with <php>constexpr</php> lambda: Since its 2017 specification "C++17", C++ provides a way to declare constant expression lambdas (equivalent to PHP's closures). This allows leveraging this feature to initialize complex values for static properties using an <php>inline</php> with <php>constexpr</php> lambda:
  
-<code>c++ +<code c++> 
-====== include <iostream> ====== +#include <iostream> 
-====== include <vector> ======+#include <vector>
  
 class Example { class Example {
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 </code> </code>
  
-=== Swift ===+==== Swift ====
  
 Just like C++, Swift allows properties to be initialized by the return values of closures: Just like C++, Swift allows properties to be initialized by the return values of closures:
  
-<code>swift+<code swift>
 class Example { class Example {
     static var myVar: Int = {     static var myVar: Int = {
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 The static constructor in this RFC supports two possible signatures: The static constructor in this RFC supports two possible signatures:
  
-1. <php>private static __staticConstruct();</php><br> +1. <php>private static __staticConstruct();</php>\\ 
-2. <php>private static __staticConstruct(): void;</php>+2. <php>private static __staticConstruct(): void;</php>\\
  
 Similar to the C# implementation, the static constructor can take no arguments. Similar to the C# implementation, the static constructor can take no arguments.
 +
 +===== Exception handling =====
 +The current behavior allows exceptions to be thrown from within the static constructor, and the program can recover from them. It's up to the programmer to decide how to handle this. This behavior is possible because the static constructor is called upon the usage of static properties, not when the class is loaded or linked. It's similar to throwing an exception from an existing "init" method, but **the static constructor won't be called by the engine a second time**. Just like an instance constructor can throw an exception, and if you decide to recover from it, you won't have an instance of that class.
  
 ===== Implementation notes ===== ===== Implementation notes =====
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   * Even if the method were <php>protected</php> or <php>public</php>, it would not be automatically called by the engine if not explicitly declared. Unlike the <php>__construct</php> method, the static constructor method is intentionally not copied to the correspondent "shortcut" variable dedicated to this magic method during inheritance operations (performed at the <php>do_inherit_parent_constructor</php> function of the <php>zend_inheritance.c</php> file).   * Even if the method were <php>protected</php> or <php>public</php>, it would not be automatically called by the engine if not explicitly declared. Unlike the <php>__construct</php> method, the static constructor method is intentionally not copied to the correspondent "shortcut" variable dedicated to this magic method during inheritance operations (performed at the <php>do_inherit_parent_constructor</php> function of the <php>zend_inheritance.c</php> file).
- 
  
 ===== Examples ===== ===== Examples =====
  
-= 1 - No code sharing to the child class: =+=== 1 - No code sharing to the child class: ===
 <PHP> <PHP>
 class MyClass class MyClass
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 </PHP> </PHP>
  
-= 2 - Sharing code to the child class: =+=== 2 - Sharing code to the child class: ===
 <PHP> <PHP>
 class MyClass1 class MyClass1
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 As per the voting RFC a yes/no vote with a 2/3 majority is needed for this proposal to be accepted. As per the voting RFC a yes/no vote with a 2/3 majority is needed for this proposal to be accepted.
  
-Voting started on 2024-XX-XX and will end on 2024-XX-XX. +===== Implementation ===== 
-  + 
-<doodle title="Accept Static Constructors RFC?" auth="erickcomp" voteType="single" closed="true"> +https://github.com/php/php-src/compare/master...erickcomp:php-src_static-constructor:master 
-   * Yes + 
-   * No +Note: This implementation still needs tests
-</doodle>+
  
 ===== Future scope ===== ===== Future scope =====
  
 In case any use cases for early execution of the static constructor arise (such as during class load, as implemented in C#), an opt-in mechanism for even earlier initialization can be considered. In case any use cases for early execution of the static constructor arise (such as during class load, as implemented in C#), an opt-in mechanism for even earlier initialization can be considered.
- 
  
 ===== References ===== ===== References =====
-Composer's ClassLoader class: <https://github.com/composer/composer/blob/main/src/Composer/Autoload/ClassLoader.php>+Composer's ClassLoader class: https://github.com/composer/composer/blob/main/src/Composer/Autoload/ClassLoader.php
  
 Java's approach on "properties" initialization: Java's approach on "properties" initialization:
-<https://docs.oracle.com/javase/tutorial/java/javaOO/initial.html>+https://docs.oracle.com/javase/tutorial/java/javaOO/initial.html
  
 Kotlin's companion objects: Kotlin's companion objects:
-<https://kotlinlang.org/docs/object-declarations.html#companion-objects>+https://kotlinlang.org/docs/object-declarations.html#companion-objects
  
 C#'s static constructors: C#'s static constructors:
-<https://learn.microsoft.com/en-us/dotnet/csharp/programming-guide/classes-and-structs/static-constructors> +https://learn.microsoft.com/en-us/dotnet/csharp/programming-guide/classes-and-structs/static-constructors
  
rfc/static_constructor.1718747143.txt.gz · Last modified: 2024/06/18 21:45 by erickcomp

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