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  1. #include <iostream>
  2.  
  3. class IBase {
  4. public:
  5.   virtual void report() const = 0;
  6.   virtual IBase * instance() const = 0;
  7. };
  8.  
  9. template <typename Derived>
  10. class Builder : public IBase {
  11. public:  
  12.   IBase *instance() const {
  13.     return new Derived;
  14.   }
  15. };
  16.  
  17. class B : public Builder<B> {
  18. public:
  19.   virtual void report() const {
  20.     std::cout << "B" << std::endl;
  21.   }
  22. };
  23.  
  24. class C : public Builder<C> {
  25. public:
  26.   virtual void report() const {
  27.     std::cout << "C" << std::endl;
  28.   }
  29. };
  30.  
  31. int main() {
  32.   IBase *b = new B;
  33.   IBase *c = new C;
  34.  
  35.   b->report();
  36.   c->report();
  37.  
  38.   IBase *b1 = b->instance();
  39.   IBase *c1 = c->instance();
  40.  
  41.   b1->report();
  42.   c1->report();
  43. }
Success #stdin #stdout 0.02s 2812KB
comments (?)
stdin 
Standard input is empty
stdout 
B
C
B
C
https://ideone.com/d4CGtv
language:
C++ (gcc 8.3)
created:
13 years ago
visibility:
secret

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