What it demonstrates

There are Template Methods, Hook Methods, pure abstract Hook Methods, i.e. Factory Methods, overloaded HookMethods and Hook Template Methods and even static HookMethods. There is also a non polymorphic NonHookMethod().

They are called in the base-class Implementation in TemplateMethod() and in the derived-class Application in TemplateHookMethod(). It demonstrates the polymorphic use of non virtual operations in different contexts:

1. context of base-class
2. context of derived-class

base-class demonstrates

• how to access the context of the derived-class (This()->) to call polymorphic methods by name shadowing, which is the static polymorphic way to call methods.

The TemplateMethod()demonstrates: call of ( all static / non static)

• a non polymorphic method via this->
• a non polymorphic redefined method, don´t do this at home!
• some polymorphic method via This()->
• a redefined polymorphic method
• a redefined overloaded polymorphic method
• a non redefined polymorphic method (indeed, calls base_type::method)
• a pure abstract defined polymorphic method
• a polymorphic template method (TemplateHookMethod)

To redefine a non polymorphic method is never a good idea, regardless of dynamic or static polymorphism. Because the effect is, you send the same message to the same object resulting in different effects, depending on the calling context: in dynamic context Base* or Derived* pointer, in static context using of this or This().

derived-class demonstrates

• how to give access to protected and private members to the base-class (friend class Implementation<Application>)
• how to give access to shadowed names of base-class (using base_type::name)

derived-class TemplateHookMethod demonstrates call of (all static / non static)

• a pure abstract method (cause it´s not declared in base-type)
• method only defined in base-class
• method defined in base-class and derived-class (overridden)
• call of base_type::method of overridden method

Further experiments

Define a member-type in base-class and redefine it in derived-class. Use method of member-type via This()->membertype::operation()