Nested classes

In ABAP OOP, we can nest classes in three ways: 

• A class as an attribute of the class
• Inheritance
• Using interfaces

Interfaces are not really a full class. This is due to the fact that, in interfaces, we have only a definition of a class without any implementation. This is important because interfaces in ABAP allow us to implement multi-inheritance. However, we'll turn to that in a moment, in the Inheritance and Interfaces section.

All examples will be shown as a global class created in SE24.

A class as an attribute of the class

We can create a class as an attribute of the class. To create that attribute, we need to add an attribute, which is typed as TYPE REF TO. In our example, we'll create...