Data Processing Process Data Tear down this Wall!!! Name is “Pat” Balance is $110 Payment is $50 Take Pat’s Balance; Subtract the Payment; Make that the Balance;
Classes & Objects OBJECT: A discrete entity with a well-defined boundary and identity that encapsulates state and behavior; an instance of a class. Rumbaugh [3 Amigos], Reference, p CLASS: The descriptor for a set of objects that share the same attributes, operations, methods, relationships and behavior. A class represents a concept within the system being Modeled. Rumbaugh [3 Amigos], Reference, p Separate the Essence from the Instance.
Class A class is a category of Things. An object is one of those things. A instantiation of a class. Encapsulation Inheritance $$ Poly m o r p h i s m Name Address Telephone CreditRating Taxonomy is a taxing task: Is a Grad student an employee? Is Pluto a Planet? Is Bill Gates human?
“Class” is perhaps Best defined by Examples… Tangible Intangible Conceptual –Cost Center, Account People Places Things Events Roles Organizations Collections of Objects Interface –Form or Dialog Infrastructure –Date, Money, Address Persistence: Database Control Reference Lists Other Systems Process –Currency Format?
They’re Everywhere! There must be a Class if … there’s a form … there’s a file … there’s a number … there are multiple copies … It’s Important NOTE-- –Sections and boxes on Forms –The name might not be obvious Responsibilities Obligation or Contract Personification Helps Know Things –Invoice: Know the Customer Do Things –Invoice: Compute Total Get Organized –Abstraction