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  1. #include <iostream>
  2.  
  3. class Interface
  4. {
  5. public:
  6.     virtual void someMethod() = 0;
  7.     virtual void someOtherMethod() const = 0;
  8. };
  9.  
  10. struct Impl : Interface {
  11.   virtual void someMethod() { std::cout << "some method\n"; }
  12.   virtual void someOtherMethod() const { std::cout << "some other method\n"; }
  13. };
  14. struct Proxy : Interface{
  15.   Proxy(Interface* i) : i(i) {}
  16.   Interface* i;
  17.   void someMethod() { std::cout << "log "; i->someMethod(); }
  18.   void someOtherMethod() const { std::cout << "log "; i->someOtherMethod(); }
  19. };
  20. class ConstProxy {
  21.   Proxy p;
  22. public:
  23.   ConstProxy(Interface const* i) : p(const_cast<Interface*>(i)) {}
  24.   void someOtherMethod() const { p.someOtherMethod(); }
  25.   operator Interface const& () { return p; }  // imitiert "extends const Interface"
  26. };
  27.  
  28. void foo( Interface& i )
  29. {
  30.   i.someOtherMethod();
  31. }
  32. void foo2( Interface const& i )
  33. {
  34.   i.someOtherMethod();
  35. }
  36.  
  37. int main()
  38. {
  39.   Impl i;
  40.   ConstProxy cp(&i);
  41.   //foo(cp);
  42.   foo2(cp);
  43. }
  44.  
Success #stdin #stdout 0s 3296KB
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Standard input is empty
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log some other method
https://ideone.com/9cmUr7
language:
C++ (gcc 8.3)
created:
12 years ago
visibility:
public

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