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  1. #include <iostream>
  2. #include <memory>
  3.  
  4. template<typename T, typename ...Args>
  5. std::unique_ptr<T> make_unique( Args&& ...args )
  6. {
  7.     return std::unique_ptr<T>( new T( std::forward<Args>(args)... ) );
  8. }
  9.  
  10. class StateManager;
  11.  
  12. class State
  13. {
  14. public:
  15.     virtual void update(StateManager &manager)= 0;
  16.     virtual ~State(){}
  17. };
  18.  
  19.  
  20.  
  21.  
  22. class StateManager
  23. {
  24. public:
  25.     void setState(std::unique_ptr<State> && newState )
  26.     {
  27.         currentState = std::move(newState);
  28.     }
  29.     std::unique_ptr<State> currentState;
  30.  
  31.     void run()
  32.     {
  33.         currentState->update(*this);
  34.     }
  35. };
  36.  
  37.  
  38. class SecondState : public State
  39. {
  40. public:
  41.     SecondState()
  42.     {
  43.         std::cout<<"CONSTRUCTOR: Second State"<<std::endl;
  44.     }
  45.  
  46.     virtual void update(StateManager &manager)
  47.     {
  48.         std::cout<<"UPDATE: Second State"<<std::endl;
  49.     }
  50.  
  51.     virtual ~SecondState()
  52.     {
  53.         std::cout<<"DESTRUCTOR: Second State"<<std::endl;
  54.     }
  55. };
  56.  
  57.  
  58. class FirstState : public State
  59. {
  60. public:
  61.     FirstState()
  62.     {
  63.         std::cout<<"CONSTRUCTOR: FirstState"<<std::endl;
  64.     }
  65.  
  66.     virtual void update(StateManager &manager)
  67.     {
  68.         std::cout<<"UPDATE: FirstState"<<std::endl;
  69.         manager.setState(make_unique<SecondState>());
  70.         std::cout<<"UPDATE-ENDING: FirstState"<<std::endl;
  71.  
  72.     }
  73.  
  74.     virtual ~FirstState()
  75.     {
  76.         std::cout<<"DESTRUCTOR: FirstState"<<std::endl;
  77.     }
  78. };
  79.  
  80.  
  81. int main()
  82. {
  83.  
  84.     StateManager manager;
  85.     manager.setState(make_unique<FirstState>());
  86.     manager.run();
  87.     manager.run();
  88.  
  89. }
Success #stdin #stdout 0s 3020KB
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Standard input is empty
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CONSTRUCTOR: FirstState
UPDATE: FirstState
CONSTRUCTOR: Second State
DESTRUCTOR: FirstState
UPDATE-ENDING: FirstState
UPDATE: Second State
DESTRUCTOR: Second State
https://ideone.com/WHLzJL
language:
C++14 (gcc 8.3)
created:
12 years ago
visibility:
public

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