crtp's Introduction

CRTP

This is a ridiculously simple library that contains a few macros.

I end up copying them into every new library I made, anyway, so I figured I would just make one library for the sake of consistency.

Consider the following example use case, which creates class templates which follow the chain Base -> Derived1 -> Derived2

/**
 * @brief Base
 */
template<typename DerivedT>
class TestInterface
{
public:
  inline void do_thing() const
  {
    CRTP_INDIRECT_M(do_wrapped_thing)();
  }

  constexpr int do_other_thing(int i)
  {
    return CRTP_INDIRECT_M(do_other_thing)(i);
  }

private:
  IMPLEMENT_CRTP_BASE_CLASS(TestInterface, DerivedT);
};


/**
 * @brief Base -> Derived1
 */
template<typename DerivedT>
class TestWrappedInterface : public TestInterface<TestWrappedInterface<DerivedT>>
{
private:
  void CRTP_OVERRIDE_M(do_wrapped_thing)() const
  {
    CRTP_INDIRECT_M(do_wrapped_thing)();
  }

  constexpr int CRTP_OVERRIDE_M(do_other_thing)(int i)
  {
    return i + i + i;
  }

  IMPLEMENT_CRTP_BASE_CLASS(TestWrappedInterface, DerivedT);
  IMPLEMENT_CRTP_DERIVED_CLASS(TestInterface, TestWrappedInterface);
};


/**
 * @brief Base -> Derived1 -> Derived2
 */
class TestDerived : public TestWrappedInterface<TestDerived>
{
public:
  TestDerived() : TestWrappedInterfaceType{} {};

private:
  void CRTP_OVERRIDE_M(do_wrapped_thing)() const
  {
    // does nothing, but compiles
  }

  IMPLEMENT_CRTP_DERIVED_CLASS(TestWrappedInterface, TestDerived);
};

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