Midterm Review

1. Be able to explain the all-caps words in the following contexts:
   • Ascii Count is a SPECIALIZATION (SUBCLASS) of Count (SUPERCLASS), which means that it INHERITS the structure and behavior of Count.
   • Count is an ABSTRACT CLASS.
   • A CountViewContainer sends messages to a particular INSTANCE of IntegerCount.
   • Interfaces in Smalltalk are constructed from MODEL, VIEW, and CONTROLLER classes.
   Discussion

2. You are creating a simulation of an engine with a particular emphasis on modeling the flow of fuel through the engine (e.g., if we were to cause a clogged fuel line, our model would show a lack of fuel to the carburetor and pistons).
   • Identify at least FOUR classes that you would need to (1) create the Problem Domain component and (2) create the Human Interface component. Identify which are which. (This does NOT have to be ALL the classes you would need, but it must be SOME of them.)
   • Using the graphical notation used in Coad and Nicola, show how your classes would relate.
   Discussion

3. Consider the Vending Machine simulation discussed in class. The list below identifies the classes which were the central ones in implementing the Vending Machine.
   • Identify which of these classes are models, which are views, and which are controllers.
   • Describe (textually) the cascade of messages which result from hitting the Select button in the CashDeviceViewContainer.

   Classes
   CashDevice
   CashDeviceViewContainer
   DisplayBox
   DisplayBoxController
   DispensingHolder
   Item
   ItemViewContainer
   ModelValueViewContainer
   

   Discussion

4. What role does inheritance have in a whole-part organization? In a specialization-generalization organization? Discussion

5. Below is one method from the Vending Machine simulation.
   • To what class does this code belong? What does it do?
   • Write a brief comment describing what each line of this code does.

   dispense: itemToDispense 
   
   	self isEmpty ifTrue: [^false].
   
   
   	(self itemIsDispensable: itemToDispense) ifFalse:
   		 [^false].
   
   
   	self printItem:  itemToDispense .
   
   
   	self activateDispenser.
   
   
   	self disconnectWithItem: itemToDispense.
   
   
   	^true
   

   Discussion

6. You have been asked to create a simulation of an airport with a particular emphasis on modeling the flow of airplanes (e.g., how long does an airplane have to wait to land or to take-off?) Identify and Describe at least FIVE classes that you would need to (1) create the Problem Domain component and (2) create the Human Interface component.
   • Be sure to identify which are Problem Domain and which are Human Interface classes.
   • Be brief, but think about what it takes to describe a class.
   Discussion

7. You are a consultant to the WhizO Toy Company ("Makers of toys for tots of all ages"). WhizO is considering a shift to an object-oriented software development process. If they do make such a shift, you're in for big bucks as the consultant who leads the way. First step is to respond to the specific concerns of the Manager of their Software Development unit:
   • "We usually have multiple teams of developers working on different parts of the programs at once. How does object-orientation help us with that?"
   • "We rely heavily on simulation when developing sophisticated toys. What would be absolutely perfect would be if we could take parts of our simulation and use it in the code for the real toy. Can we do that? How?"
   • "What happens if we develop add-ons for a toy, like a new Laser Gun for our Omega Video Game System? Or if we develop a new variation on a toy, like the Phaser Range Finder Gun (which is like the Laser Gun)? Can O-O help our productivity in doing this?"
   Discussion

8. Okay, you've sold them. WhizO is now starting several software development projects using an object-oriented approach. You've been hired as the Answer Person for the teams. Help the programmers with these problems:
   • Hi! I'm working on the video game 'Attack of the Killer Rambo Clones'. My Rambo clones will each have their own assault rifle. I need a method which jams the assault rifle when it overheats due to prolonged use. Should jamRifle be a Class or an Instance method? What's the difference?
   • Yeah, I'm doing the new 'Tommy the Talker' doll which talks to the user, and I've got several services that I'm trying to decide if they're part of the problem domain or the human interface domain. Can you give me a hand?

     - Method to listen for the user's name.
     - Method to choose a phrase which is appropriate for the current conversation context.
     - Method to ask the user's name.
     - Method to decide when to pause in the conversation.
     

   Discussion