Connie's Convenience Store - About Peter Coad

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80 Connie’s Convenience Store Working Out Human-Interaction Dynamics with Scenarios Hold it! A sale window needs to know its values for a payment. Add a payment attribute. “Complete the sale” scenario Here is the scenario view (Figure 1–55): SaleWindow endSale open updateBalance Figure 1–55: The “complete the sale” scenario view. Scenario: log off One more time. Here is the scenario view (Figure 1–56): SaleWindow CashDrawer Store endSale saleWindow.endSale open updateBalance Session logoff endSession logoff saleWindow.logoff endSession addSale addSale Figure 1–56: The “log off” scenario view. Scenario: actual cashier logs off. Scenario constraint: 0.1 seconds, 9 out of 10 times, 1 second max. session.endSession Scenario: completes the sale. Another service! Add “end session” to session. Way to go! This object model is really beginning to take shape. Scenarios drive you to significant detail—and better object models. Cool! Scenario constraint: 0.1 seconds, 9 out of 10 times, 0.5 seconds max. cashDrawer.open cashDrawer.updateBalance (total ; ) store.addSale (sale ; )
Selecting System-Interaction Objects Connie’s Convenience Store 81 SELECTING SYSTEM-INTERACTION OBJECTS Interaction with other systems. #33. “Select Interacting Systems or Devices” Strategy selecting objects (model components) • Select it. Look for other systems and pieces of equipment that your system must interact with. Look for interacting systems; look for devices needing data acquisition and control. (Skip display or printing “nuts and bolts.”) • Examples: aileron, avionics system, controller, diverter, elevator, radar, rudder, sensor, scanner. • Model it. With a problem-domain object, and With a corresponding system-interaction (SI) object, encapsulating low-level communication detail. You need to interact with an authorization system. Add a problem-domain object: authorization system. Now add a system-interaction object, to encapsulate low-level communication needs: authorization system SI (Figure 1–57): ProblemDomain AuthorizedPayment AuthorizationSystem Cash CashDrawer Cashier Charge Check Item Payment Person PromoPrice Register ReturnLineItem Sale SaleLineItem Session Store TaxCategory SystemInteraction AuthorizationSystemSI AuthorizationSystem AuthorizationSystemSI Figure 1–57: Selecting system interaction objects.
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GETTING STARTED 1 Connie’s Conven
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Identifying System Purpose and Feat
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Selecting Objects Connie’s Conven
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Selecting Problem-Domain Objects Co
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Applying Patterns: Select and Organ
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Connie's Convenience Store - About Peter Coad

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