Class adapter pattern in the classic TimedDoor case study

Question

In Uncle Bob's classic tutorial on ISP, he presents a case study on a timed security door. Martin suggests two possible designs for combining the TimerClient with the Door hierarchy:

An Object Adapter pattern:

A Class Adapter pattern:

My question is how to interpret the Class Adapter. Who is the adapted interface, who is the adapter and who is the adaptee? There are two options that can I think of:

• The Door is the adaptee, and the TimedDoor is the adapter. This conforms with the structure of the Class Adapter pattern, as the adapter inherits from the two abstract classes.
• The TimedDoor is both the adapter and adaptee. This is consistent with the Object adapter solution, with a "shortcut", combining the adapter and adaptee together.

Can you clarify this point?

Answer 1

The UML diagrams from page 141 of the GoF book include appropriate labels.

So your first bullet is closer: the Target is whichever interface the Client knows and uses; the Adaptee is whichever interface gets called by the Adapter. If the Client knows and uses both interfaces, you can have a two-way Adapter where Target and Adaptee are interchangeable.