Basic Design Principles

Model/View/Controller design pattern

• The model is the underlying data structure. It should contain no GUI code of any sort.
• The view constructs a graphical representation from the model.
• The controller changes the model (and, implicitly, the view) based on input.

Inspection and Mutation

• An inspector method delivers information about an object without changing it.
• A mutator method changes an object.
• A mutable class contains mutators.
• An immutable class contains only inspectors.
• Questions:
  1. Can a single method be both an inspector and a mutator? What would be the advantages and disadvantages of this?
  2. Would it ever make sense to create a class without inspectors? Do most classes need inspectors?
  3. Under what circumstances would an immutable class be helpful?

Other topics

• Cohesion: Each class and method should do one thing, and do it well.
• Law of Demeter: Avoid chained method invocations. These can be avoided by delegating.
• Methods should be written at a single level of abstraction.