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  1. #include <iostream>
  2. #include <vector>
  3. #include <algorithm>
  4. #include <functional>
  5.  
  6. //========================================================================
  7. //Reference-wrapping utility functions:
  8.  
  9. /*template<class ContainerType, class ElementType = typename ContainerType::value_type >
  10. std::vector<std::reference_wrapper<ElementType>> RefWrapAsVector(ContainerType &container)
  11. {
  12. 	//Create a vector of std::reference_wrappers wrapping 'ElementType'
  13. 	return std::vector<std::reference_wrapper<ElementType>>(std::begin(container), std::end(container));
  14. }*/
  15.  
  16. //And the const version:
  17. template<class BaseType, class ContainerType>
  18. std::vector<std::reference_wrapper<const BaseType>> RefWrapAsVector(const ContainerType &container)
  19. {
  20. 	//Create a vector of std::reference_wrappers wrapping 'BaseType'.
  21. 	return std::vector<std::reference_wrapper<const BaseType>>(std::begin(container), std::end(container));
  22. }
  23.  
  24.  
  25. //========================================================================
  26. //Your classes:
  27.  
  28. class Animal
  29. {
  30. 	public:
  31.     virtual void Talk() const { std::cout << "<generic animal noise>" << std::endl; }
  32. };
  33.  
  34. class Cat : public Animal
  35. {
  36. 	public:
  37. 	Cat(std::string text) : kittySpeach(text) { }
  38.  
  39. 	void Talk() const override  { std::cout << kittySpeach << std::endl; }
  40.  
  41. 	private:
  42. 	std::string kittySpeach;
  43. };
  44.  
  45.  
  46. void ForceAnimalsToTalk(const std::vector<std::reference_wrapper<const Animal>> &animals)
  47. {
  48. 	for(const Animal &animal : animals)
  49. 	{
  50. 		animal.Talk();
  51. 	}
  52. }
  53.  
  54. //========================================================================
  55.  
  56. int main()
  57. {
  58. 	//Really just an excuse to add moar cats to teh code.
  59. 	std::vector<Cat> myCats = {Cat("Meow"), Cat("Purr"), Cat("Meowmeow"), Cat("*yawns adorably*")};
  60.  
  61. 	ForceAnimalsToTalk(RefWrapAsVector<Animal>(myCats));
  62.  
  63. 	return 0;
  64. }
Success #stdin #stdout 0s 3232KB
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Standard input is empty
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Meow
Purr
Meowmeow
*yawns adorably*
https://ideone.com/meCnf5
Demonstrating taking vectors of reference-wrapped base classes to build functions for arbitrary numbers of polymorphic classes.
language:
C++14 (gcc 8.3)
created:
8 years ago
visibility:
public

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