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  1. #include <iostream>
  2. #include <memory>
  3.  
  4. struct A {
  5. 	A() {
  6. 		std::cout << "Constructor" << std::endl;
  7. 	}
  8. 	A(const A&) noexcept {
  9. 		std::cout << "Copy constructor" << std::endl;
  10. 	}
  11. 	A(A&&) noexcept {
  12. 		std::cout << "Move constructor" << std::endl;
  13. 	}
  14. };
  15.  
  16. struct onlyMovable {
  17. 	onlyMovable() = default;
  18. 	onlyMovable(onlyMovable&&) = default;
  19. 	onlyMovable(const onlyMovable&) = delete; // Запрещаем копирование объекта
  20. };
  21.  
  22. struct B {
  23. 	B(A) {}
  24. 	B(onlyMovable) {}
  25. };
  26.  
  27. template <typename T, typename... Args>
  28. std::shared_ptr<T>
  29. factory1(Args... args)                                       
  30. {
  31.     return std::shared_ptr<T>(new T(std::forward<Args>(args)...));
  32. }
  33.  
  34. template <typename T, typename... Args>
  35. std::shared_ptr<T>
  36. factory2(Args... args)                                       
  37. {
  38.     return std::shared_ptr<T>(new T(args...));
  39. }
  40.  
  41. int main() {
  42.  
  43. 	std::cout << "---------------------------------" << std::endl;
  44. 	std::cout << "With std::forward" << std::endl;
  45. 	auto p1 = factory1<B>(A());
  46. 	std::cout << "---------------------------------" << std::endl;
  47. 	std::cout << "Without std::forward" << std::endl;
  48. 	auto p2 = factory2<B>(A());
  49. 	std::cout << "---------------------------------" << std::endl;
  50.  
  51.  
  52. 	auto p3 = factory1<B>(onlyMovable()); 
  53. 	//auto p4 = factory2<B>(onlyMovable()); // Ошибка компиляции, копировать этот объект нельзя
  54. }
Success #stdin #stdout 0s 4336KB
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stdin
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Standard input is empty
stdout
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---------------------------------
With std::forward
Constructor
Move constructor
---------------------------------
Without std::forward
Constructor
Copy constructor
---------------------------------
https://ideone.com/WWZhhL
language:
C++14 (gcc 8.3)
created:
5 years ago
visibility:
secret

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