Connie's Convenience Store - About Peter Coad

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36 Connie’s Convenience Store Establishing Responsibilities for Problem-Domain Objects Model it. Cashier number password authorizationLevel currentSession isAuthorized assessPerfOverInterval Figure 1–23: Cashier: “what I do.” Participant: customer Connie has already decided to hold off on finding a way to know about specific customers. Yet, what if you had a customer object? It could do some interesting things for you, though. #88. “Why, Why, Why” Strategy establishing responsibilities / what I do (fundamentals) • Add value by asking “why, why, why?” Why, why, does the system need this object anyway? What useful questions can it answer? What useful actions can it perform? What is done to an actual object, something that this object could do itself? It’s the active side of objects that’s the exciting aspect; the active side tells you more about the “why, why, why” of having that object in the object model. A customer object could: – tally purchases over interval – tally purchase rate over interval – tally number of returns over interval – tally number of bad checks over interval. Such services all fall under one important heading, “assess customer” or “qualify customer.” Note: “assess” is a stereotypical behavior for a participant; look for “assess” services whenever you consider the active side of a participant object. Responsibilities for places Store Why do you need a store object? Yes, you could keep track of the name, address, and other attribute values for a store.
Establishing Responsibilities for Problem-Domain Objects Connie’s Convenience Store 37 More importantly, a store object gives you a place to put those calculations that apply across a collection of what a store contains: registers, items, and cashiers. #102. “Service across a Collection” Strategy establishing responsibilities / what I do (where to put) • Service across a collection of objects? Add a service to a collection object, an object that knows and does things across that collection. Let each worker within a collection do its fair share—as much as it can, based upon what it knows. • Be sure the collection does just those things that apply across a collection; makes its workers do as much work as they know enough to accomplish. • Across its workers: enforce business rules that may apply to its participation. Establish responsibilities: “what I know.” #53. “Establish Place Attributes” Strategy establishing responsibilities / what I know (pattern players) • For location, include: number, name, address (perhaps latitude, longitude, altitude). Just include the name of the store; that’s enough for now. – name. Establish responsibilities: “who I know.” #75. “Establish Place Object establishing responsibilities / Connections” Strategy who I know (pattern players) • For a location, include object connections to objects which come to rest at a location . . . or are contained by a location. • For a location, include object connections to transaction objects, to show that location’s participation in that transaction. Who does a store object know? A store object, as a container, knows its contents: – registers (zero or more) – items (zero or more) – cashiers (zero or more).
Page 1 and 2: GETTING STARTED 1 Connie’s Conven
Page 3 and 4: Identifying System Purpose and Feat
Page 5 and 6: Selecting Objects Connie’s Conven
Page 7 and 8: Selecting Problem-Domain Objects Co
Page 19 and 20: Applying Patterns: Select and Organ
Page 29 and 30: Establishing Responsibilities for P
Page 35: Establishing Responsibilities for P
Page 55 and 56: Applying Patterns: Establish Proble
Page 61 and 62: Working Out Problem-Domain Dynamics
Page 63 and 64: Working Out Problem-Domain Dynamics
Page 65 and 66: Scenario: sale calculates its total
Page 67 and 68: Selecting Human-Interaction objects
Page 69 and 70: Establishing Human Interaction Resp
Page 71 and 72: Establishing Human Interaction Resp
Page 73 and 74: Working Out Human-Interaction Dynam
Page 75 and 76: Scenario: actual cashier logs on. S
Page 77 and 78: Scenario: sell item. Receipt SaleLi
Page 79 and 80: Scenario: get payment by check Rece
Page 81 and 82: Selecting System-Interaction Object
Page 83 and 84: Establishing System-Interaction Res
Page 85 and 86: Working Out System-Interaction Dyna
Page 87 and 88:
Selecting Data-Management Objects a
Page 89 and 90:
Working Out Data-Management Dynamic
Page 91 and 92:
Progress at This Point Connie’s C
Page 93 and 94:
Progress at This Point Connie’s C
Page 95:
Wrap Up Connie’s Convenience Stor
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Connie's Convenience Store - About Peter Coad

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