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  1. #include <memory>
  2. #include <typeindex>
  3. #include <iostream>
  4. #include <string>
  5. #include <vector>
  6. #include <map>
  7.  
  8. typedef std::multimap<std::type_index, void*> Object;
  9. typedef std::map<Object, std::shared_ptr<void>> ObjectCollection;
  10.  
  11. Object object;
  12. ObjectCollection objectCollection;
  13.  
  14. template<typename T, typename... Args>
  15. T* getResource(Args&& ... args)
  16. {
  17. 	// Creating tuple from the arguments
  18. 	std::tuple<Args...> currentArgs(std::forward<Args>(args)...);
  19. 	// Getting object type info
  20. 	std::type_index type = { typeid(T) };
  21.  
  22. 	// Getting all objects from the collection that are of the same type
  23. 	auto range = object.equal_range(type);
  24.  
  25. 	for (auto it = range.first; it != range.second; ++it)
  26. 	{
  27. 		// it->second is a void* Since we are iterating through
  28. 		// the the collection of the same type I'm trying to cast
  29. 		// back. Object construct parameters should be the same 
  30. 		// (in this example: const std::string &fileName)
  31. 		auto storedArgs = *static_cast<std::tuple<Args...>*>(it->second);
  32.  
  33. 		// >>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>
  34. 		// Problem is here. currentArgs and storedArgs are always equal :/
  35. 		// >>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>
  36. 		// Return the object from the collection if current arguments and
  37. 		// arguments from the collection are the same
  38. 		if (currentArgs == storedArgs)
  39. 		{
  40. 			std::cout << "Found... returning..." << std::endl;
  41. 			// found... return...
  42. 			return static_cast<T*>(objectCollection[object].get());
  43. 		}
  44. 	}
  45.  
  46. 	// Object with the same arguments were not found
  47. 	// Adding to collection and return
  48. 	std::cout << "Adding to collection..." << std::endl;
  49. 	object.emplace(type, &currentArgs);
  50. 	objectCollection[object] = std::make_shared<T>(std::forward<Args>(args)...);
  51. 	return static_cast<T*>(objectCollection[object].get());
  52. }
  53.  
  54. class Resource
  55. {
  56. public:
  57. 	virtual ~Resource() = default;
  58.  
  59. 	template<typename T, typename... Args>
  60. 	static T* get(Args&& ... args)
  61. 	{
  62. 		return getResource<T>(std::forward<Args>(args)...);
  63. 	}
  64. };
  65.  
  66. class Image
  67. {
  68. public:
  69. 	Image(const std::string &fileName)
  70. 	{
  71. 		std::cout << "Loading image " << fileName.c_str() << std::endl;
  72. 	}
  73.  
  74. 	~Image(){};
  75. };
  76.  
  77. int main()
  78. {
  79. 	auto image1 = Resource::get<Image>("aaa.jpg");
  80. 	auto image2 = Resource::get<Image>("bbb.jpg");
  81. 	auto image3 = Resource::get<Image>("aaa.jpg");
  82. 	//getchar();
  83. }
Success #stdin #stdout 0s 3472KB
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stdin
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Standard input is empty
stdout
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Adding to collection...
Loading image aaa.jpg
Found... returning...
Found... returning...
https://ideone.com/h3yzvy
language:
C++14 (gcc 8.3)
created:
8 years ago
visibility:
public

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