C++ “Interfaces”

Bringing It All Together

See also

• Inheritance Basics

• Inheritance: private, protected (Implementation Inheritance)

• Virtual Methods

• Polymorphic Usage Of Objects

• Destructors And Inheritance

• Virtual Destructors

• C++ has a toolset for

  • Inheritance

  • Dynamic dispatch

• Does not make any policies

• Java does

  • interface, implements: interfaces (C++: pure virtual) and their implementation

  • extends: implementation inheritance (see Inheritance: private, protected (Implementation Inheritance))

• Programmer’s choice how to use tools

• ⟶ very easily incomprehensible code is created

• ⟶ best practices!

Interfaces

See also

• override

• final

Bringing it all together: an interface is defined like so …

• Virtual destructor, with an empty implementation (remember, destructors cannot be abstract/pure virtual)

• Only abstract/pure virtual methods

class Interface
{
public:
    virtual ~Interface() {}
    virtual void method() const = 0;
};

• Ideally nothing else

• Programmers are invited to break the rules!

• ⟶ Hybrid forms, e.g. providing little helper methods in the interface’s protected interface

• ⟶ Personal taste, combined with respect for colleagues

Note

C++11 brings features for derived classes:

• override

• final