Curiously Recurring Template Pattern - cppreference.com (original) (raw)

The Curiously Recurring Template Pattern is an idiom in which a class X derives from a class template Y, taking a template parameter Z, where Y is instantiated with Z = X. For example,

template class Y {};   class X : public Y {};

[edit] Example

CRTP may be used to implement "compile-time polymorphism", when a base class exposes an interface, and derived classes implement such interface.

#include   #ifndef __cpp_explicit_this_parameter // Traditional syntax   template struct Base { void name() { static_cast<Derived*>(this)->impl(); } protected: Base() = default; // prohibits the creation of Base objects, which is UB }; struct D1 : public Base { void impl() { std::puts("D1::impl()"); } }; struct D2 : public Base { void impl() { std::puts("D2::impl()"); } };   #else // C++23 deducing-this syntax   struct Base { void name(this auto&& self) { self.impl(); } }; struct D1 : public Base { void impl() { std::puts("D1::impl()"); } }; struct D2 : public Base { void impl() { std::puts("D2::impl()"); } };   #endif   int main() { D1 d1; d1.name(); D2 d2; d2.name(); }

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[edit] See also

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