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  1. #include <iostream>
  2. #include <memory>
  3. #include <functional>
  4.  
  5. using namespace std;
  6.  
  7. struct cleanup {
  8. 	void operator() (int *i) {
  9. 		std::cout << "Cleaning up resource: " << i << "(" << *i << ")"
  10. 		          << std::endl;	
  11.         // Do the work for releasing resource
  12.         delete i;
  13. 	}
  14. };
  15.  
  16. void use_temporary_resource(std::shared_ptr<int> resource,
  17.                             const int &proof, const int &multiple) {
  18. 	int &i = *resource;
  19. 	std::cout << "Proof " << proof << ", using the resource: " << i << std::endl;
  20. 	std::cout << i << "*" << multiple << "=" << i*multiple << std::endl;
  21. }
  22.  
  23. int main() {
  24. 	std::shared_ptr<int> tempResource1(new int(1), cleanup());
  25. 	std::cout << "Resource 1 created: " 
  26. 	          << tempResource1.get() << "(" << *tempResource1 << ")" << std::endl;
  27.  
  28. 	// Resource is held onto with bind
  29. 	std::function<void(int i)> proof1 = std::bind(use_temporary_resource,
  30. 	                                              tempResource1,
  31. 	                                              1,
  32. 	                                              std::placeholders::_1);
  33.     // If it wasn't this would close the resource
  34.     tempResource1.reset();
  35.     proof1(1);
  36.     proof1(2); 
  37. 	{
  38. 	std::shared_ptr<int> tempResource2(new int(2), cleanup());
  39. 	// Resource is held onto with bind
  40. 	std::function<void(int i)> proof2 = std::bind(use_temporary_resource,
  41. 	                                                tempResource2,
  42. 	                                                2,
  43. 	                                                std::placeholders::_1);
  44. 	// If it wasn't this would close the resource
  45.     tempResource2.reset();
  46.     proof2(10);
  47.     proof2(20);
  48. 	}  // Once scope goes away from proof2, the resource is released.
  49. 	std::cout << "Resource 2 should have been released after exiting scope containing proof2 (here)."
  50. 	          << std::endl;
  51.  
  52. 	std::shared_ptr<int> tempResource3(new int(3), cleanup());
  53. 		std::cout << "Resource 3 created: " 
  54. 	              << tempResource3.get() << "(" << *tempResource3 << ")" << std::endl;
  55. 	// Show that normally a resource will disapear if not placed in bind
  56. 	tempResource3.reset();
  57. 	std::cout << "Exiting..."  << std::endl; 
  58. 	return 0;
  59. }
  60.  
Success #stdin #stdout 0s 3436KB
comments (?)
stdin 
Standard input is empty
stdout 
Resource 1 created: 0x94b7008(1)
Proof 1, using the resource: 1
1*1=1
Proof 1, using the resource: 1
1*2=2
Proof 2, using the resource: 2
2*10=20
Proof 2, using the resource: 2
2*20=40
Cleaning up resource: 0x94b7048(2)
Resource 2 should have been released after exiting scope containing proof2 (here).
Resource 3 created: 0x94b7048(3)
Cleaning up resource: 0x94b7048(3)
Exiting...
Cleaning up resource: 0x94b7008(1)
https://ideone.com/yIsg1E
language:
C++14 (gcc 8.3)
created:
10 years ago
visibility:
public

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