SElec-6 Design

SElec-6 Design - LECTURE 6: Object Oriented Design Ivan...

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Ivan Marsic Rutgers University LECTURE 6: Object Oriented Design
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2 Topics Assigning Responsibilities to Objects Design Principles Expert Doer High Cohesion Low Coupling Business Policies Class Diagram
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3 select function(“unlock") : System User «initiating actor» prompt for the key enter key verify key signal: valid key, lock open open the lock, turn on the light Timer «offstage actor» start ("duration“) System Sequence Diagrams considered interactions between the actors We already worked with interaction diagrams: System Sequence Diagrams System Sequence Diagrams
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4 Design: Object Interactions • System Sequence Diagrams considered interactions between the actors Object Sequence Diagrams consider interactions between the objects checkKey() sk := getNext() alt Controller : LockCtrl setOpen(true) : Checker : KeyStorage val == null : setLit(true) val != null [else] select function(“unlock") : System User «initiating actor» prompt for the key enter key verify key signal: valid key, lock open open the lock, turn on the light Timer «offstage actor» start ("duration“) ystem System Sequence Diagram Design Sequence Diagram
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5 Metaphor for Software Design: “Connecting  the Dots” :Notifier :DatabaseConn Database Landlord Resident :Archiver :Controller :SearchRequest :InterfacePage :PageMaker :InvestigRequest We start with objects/concepts from the Domain Model and modify or introduce new objects, as needed to make the system function work.
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6 Types of Object Responsibilities Knowing responsibility : Memorizing data or  references, such as data values, data collections, or references  to other objects, represented as a property Doing responsibility : Performing computations, such as  data processing, control of physical devices, etc., represented as  a method Communicating responsibility : Communicating  with other objects, represented as message sending (method  invocation)
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7 Design: Assigning Responsibilities (a) (b) : PageMaker : DatabaseConn accessList := retrieve(params : string) interfacePage := render(accessList : string) ? ?
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SElec-6 Design - LECTURE 6: Object Oriented Design Ivan...

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