CRTP Corriously Recuring Template Pattern

this is a strange name, but it means inherit from a template and the argument is the class itself!
class Application : public Implementation<Application>{..};

Name shadowing vs. virtual

The derived type Application is known at compile-time in the base-class Implementation via template parameter ConcreteApplication. Hence this can be static casted: static_cast<ConcreteApplication*>(this) done in Method This(). To make clear what it is, the alias using this_type = ConcreteApplication; is defined and used in the cast instead of the name of the parameter.

To access a member of a template use this->, but this is the scope of the class where it´s used, in this case Implementation<Application>.

To access a member of the derived class Application, use This()-> which casts this to this_type as described above. Because This() is of type Application*const, the name resolution starts in that scope with the consequence, all names from the outer scope e.g. the base-class are hidden, if the name is used in any way in the derived-class.

With using base_type = Implementation<Application>; we can have a using declaration using base_type::name, which expands the scope, where the name is searched for.

With this in place in the derived-class, the name of e.g. a overloaded method witch one of them is overridden in the derived-class, the overloads from base-class will be found.

This()->overloadedAndOverriddenMethod(42) in this Version named HookMethod2(int) with an overload HookMethod2() which is overridden in Application and called in base-class Implementation::TemplateMethod().

Template Method Pattern with CRTP