fork(1) download
copy 
  1. #include <iostream>
  2. #include <memory>
  3. #include <vector>
  4.  
  5. using namespace std;
  6.  
  7.  
  8. /////////////////////////////////////////
  9. // opengl_helper.h
  10. // this is some manager class that knows what should be initialized later
  11. struct OpenGLHelper
  12. {
  13. 	typedef std::function<void()> function_type;
  14.  
  15. 	static void register_initializer(function_type fn);
  16.  
  17. 	static std::vector<function_type> *initializer_list;
  18.  
  19. 	static void run_init();
  20. };
  21. // helper class that will register some function at construction time
  22. struct OpenGLHelper_initializer
  23. {
  24. 	OpenGLHelper_initializer(OpenGLHelper::function_type fn)
  25. 	{
  26. 		OpenGLHelper::register_initializer(fn);
  27. 	}
  28. };
  29. /////////////////////////////////////////
  30. //opengl_helper.cpp
  31. // static pointer to a list
  32. // it will be initialized by nullptr when program loads
  33. // this is important to use raw pointer as it does not need to call any constructor
  34. std::vector<OpenGLHelper::function_type> *OpenGLHelper::initializer_list = nullptr;
  35.  
  36. // function that puts initializer into a list. 
  37. void OpenGLHelper::register_initializer(OpenGLHelper::function_type fn)
  38. {
  39. 	if (!initializer_list)
  40. 		initializer_list = new std::vector<OpenGLHelper::function_type>;
  41.  
  42. 	initializer_list->push_back(fn);
  43. }
  44.  
  45. void OpenGLHelper::run_init()
  46. {
  47. 	if (initializer_list)
  48. 	{
  49. 		for (auto fn : *initializer_list)
  50. 			fn();
  51. 	}
  52. }
  53.  
  54. /////////////////////////////////////////
  55. // figure.h
  56. // here is sample class that will be registered for initialization
  57. struct Square
  58. {
  59. 	static int to_be_initialized;
  60.  
  61. 	// static member that will register Square class to be initialized
  62. 	static OpenGLHelper_initializer __initializer;
  63. };
  64.  
  65. /////////////////////////////////////////
  66. // Square.cpp
  67. int Square::to_be_initialized = 0;
  68. // this is the most interesting part - register square into initializer list
  69. OpenGLHelper_initializer Square::__initializer([](){
  70. 	Square::to_be_initialized = 15; 
  71. 	std::cout << "Called Square::init: " << to_be_initialized << std::endl; 
  72. });
  73.  
  74. int main() 
  75. {
  76. 	std::cout << "Before initialization : " << Square::to_be_initialized << std::endl;
  77. 	OpenGLHelper::run_init();
  78. 	std::cout << "After  initialization : " << Square::to_be_initialized << std::endl;
  79. 	return 0;
  80. }
Success #stdin #stdout 0s 3472KB
comments (?)
stdin
copy 
Standard input is empty
stdout
copy 
Before initialization : 0
Called Square::init: 15
After  initialization : 15
https://ideone.com/6MuykR
language:
C++14 (gcc 8.3)
created:
7 years ago
visibility:
public

Share or Embed source code

Discover > Sphere Engine API

The brand new service which powers Ideone!

Discover > IDE Widget

Widget for compiling and running the source code in a web browser!