COMP 310 Fall 2012	Lec35: Design Almost Post-Mortem

HW08 is due Wed. Nov. 16, 2012 @ 1 PM.

Testing session tonight @ 7 PM:  Meet outside of DH 1064 and we will find an open room.

Outstanding design issues:

• What should be the type of the input parameter to the data packet execute() method, which is also the input parameter type for the data packet visitor's caseAt() method and its commands' apply() methods?  
• Can the getUser() method on many data packet types be removed since the data packet itself already has the sender's stub?

Implemenation Issues:

• Adding yourself to a chat room safely -- don't want to receive your own IAddUser packet!
• How to insure that the processing of a datapacket has completed for all users.

Let's spend today's lecture hour dissecting the ChatApp design for both its strengths and weaknesses:

The Hardest Parts:

• Hardest to design?
• Hardest to understand?
• Hardest to code?
• Hardest to debug?

Issues to consider

• How did the design decision affect the program as a whole?  
  • Was it a positive or negative impact?
  • Did it make the system simpler or more complex?
  • Did it make coding easier or harder?
  • Were you coding with or against the paradigm, i.e. did it help or hinder your ability to express your ideas?
  • Did it make the system more/less
    • flexible
    • extensible
    • robust
    • correct
• What were the alternatives?
• Overall, was it the right decision?
  • What were the compromises?

Starting Points for Discussion:

• Use of extended visitors
  • Overall effect on system
    • For datapackets
    • For status
  • ICmd2ModelAdapter interface
    • Available services
• IHost
  • Is receiveIHost() necessary?
• IChatRoom
  • No Add/RemoveAllUsers?
  • Lack of model access.
• IUser
  • Should one be able to get the IP address of an IUser?
• Threading issues

Class Discussion Synopsis:

© 2012 by Stephen Wong