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  1. #include <iostream>
  2.  
  3. void doSomething (int x) {std::cout << "Do something with " << x << std::endl;}
  4.  
  5. template <typename T, typename D>
  6. void helper(const D& base)
  7.  {
  8.     // Code A
  9.     if (base.T::foo() < 6) {
  10.         // Code B
  11.     }
  12.     doSomething (base.T::goo());
  13.     // Code C
  14.     if (base.T::hoo() > 10) {
  15.         // Code D
  16.     }
  17. }
  18.  
  19. struct Base {
  20.     virtual ~Base() = default;
  21.     virtual int foo() const {return 5;}
  22.     virtual int goo() const {return 6;}
  23.     virtual int hoo() const {return 7;}
  24.  
  25.     void noTemplatePattern() const
  26.     {
  27.         helper<Base>(*this);
  28.     }
  29. #if 0 // activate this code if you want this method accessible from base
  30.     virtual void templatePattern() const = 0;
  31. #endif
  32. };
  33.  
  34. template <typename Derived>
  35. struct BaseImpl : Base {
  36. 	void templatePattern() const /*override final*/ {
  37.     	helper<Derived>(static_cast<const Derived&>(*this));
  38. 	}
  39. };
  40.  
  41. struct Derived : BaseImpl<Derived> {
  42.     virtual int foo() const override {return 12;}
  43.     virtual int goo() const override {return 13;}
  44.     virtual int hoo() const override {return 14;}
  45. };
  46.  
  47. int main() {
  48.     Derived d;
  49.     d.noTemplatePattern();
  50.     d.templatePattern();
  51. }
  52.  
Success #stdin #stdout 0s 3296KB
comments (?)
stdin
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Standard input is empty
stdout
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Do something with 6
Do something with 13
https://ideone.com/kAATlX
language:
C++14 (gcc 8.3)
created:
11 years ago
visibility:
secret

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