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  1. #include <iostream>
  2. #include <stdexcept>
  3.  #include <typeinfo>
  4.  
  5. class Committer
  6. {
  7. public:	
  8.  
  9. 	template <typename T>
  10. 	void mark_var_change(T *var)
  11. 	{
  12. 	    mPointer = var;
  13. 	    mTypeInfo = &typeid(T*);
  14. 	}
  15.  
  16. 	template <typename T>
  17. 	void commit_change(T new_value)
  18. 	{
  19. 		if (*mTypeInfo != typeid(T*)) {
  20. 		    throw std::runtime_error("Bad type");
  21. 		}
  22. 		if (mPointer == nullptr) {
  23. 			throw std::runtime_error("nullptr was stocked");
  24. 		}
  25. 	    *reinterpret_cast<T*>(mPointer) = new_value;
  26. 	}
  27.  
  28. private:
  29.     void* mPointer = nullptr;
  30.     const std::type_info* mTypeInfo = nullptr;
  31. };
  32.  
  33.  
  34. int main() {
  35. 	Committer c;
  36. 	int i;
  37. 	float f;
  38.  
  39. 	c.mark_var_change(&i);
  40. 	c.commit_change(42);
  41.  
  42. 	c.mark_var_change(&f);
  43. 	c.commit_change(4.2f);
  44.  
  45. 	std::cout << i << " " << f << std::endl;
  46.  
  47. 	try
  48. 	{
  49. 		c.mark_var_change(&i);	
  50. 		c.commit_change(4.2f);	
  51. 	}
  52. 	catch (const std::exception&e)
  53. 	{
  54. 		std::cout << e.what() << std::endl;
  55. 	}
  56. }
  57.  
  58.  
Success #stdin #stdout 0s 3232KB
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stdin
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Standard input is empty
stdout
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42 4.2
Bad type
https://ideone.com/VaIHQD
language:
C++14 (gcc 8.3)
created:
8 years ago
visibility:
public

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