Object as Student

Conceptual Advantage

Mapping

PL	NM
class	natural language description of methods and their behaviors (on sheet of paper)
object	student
method call	verbal request made to student
actual argument	stated as part of verbal request
return value	verbal response from student

Draws Attention To

Objects, method calls, and returns.

Use When

When the meaning of OO is still unclear.

Cost

Difficult for instructor to react to students' actions during role-play,and to catch (and exploit) all the teachable moments.

Details

This idea is based on Andrianoff & Levine’s Role Playing in an OO World.

Matthias Hauswirth uses this notional machine in the first week of his object-oriented programming course. The course follows an objects-first methodology, and object creation and method invocation are the first concepts students learn.

This analogy-based notional machine has two main risks:

• Students may believe that objects—like students—are independent active entities
• Students may believe that method calls are asynchronous (non-blocking), i.e., that the caller continues operating while waiting for the callee’s response