Connie's Convenience Store - About Peter Coad

More documents

Recommendations

Info

56 Connie’s Convenience Store Applying Patterns: Establish Problem-Domain Responsibilities Collection-worker Consider the fundamental pattern of object modeling: collection-worker. #1. “Collection-Worker” Pattern the fundamental pattern • Collection-worker is the fundamental object-model pattern. • All other object-model patterns are variations on this theme. • Typical object interactions howMany —> calcForMe calcOverWorkers —>calcForMe howMuch —> calcForMe rankWorkers —>rateMe • Other notes “aboutMe” helps one think about what other attributes might be needed “calcForMe” helps one think about what specific calculations might be needed “rankMe” helps one think about what ordering or comparrison services might be “rateMe” helps one think about what self-assessment services might be needed A collection object knows about some number of workers. A collection object only does those things which apply across its collection of workers, e.g., it calculates, rates, and selects. A worker does all that it can do with what it knows, or with what others may tell it in combination with what it knows. How do you find places to apply a pattern? Just look for potential pattern players! In this case, look for objects that know some number of objects. Such a “knowing” is indicated with an object connection (or a special kind of object connection, a wholepart connection) that has an upper-bound constraint of “many.” Many patterns are collection-worker patterns. Apply some here. Participant-transaction number name date time status aboutMe Collection howMany howMuch rankWorkers calcOverWorkers calcForMe n 1 number name aboutMe Worker calcForMe rateMe Okay, you worked with this one a bit earlier. Consider cashier and session. A cashier object knows all of the sessions it has participated in. So a cashier object is the logical place to put any service that needs to do something across such a collection of sessions. For example, you could ask a cashier object to calculate the quantity sold over a specified interval. You could also let a cashier object calculate its total amount of sales made over a specified interval. Hence:
Applying Patterns: Establish Problem-Domain Responsibilities Connie’s Convenience Store 57 – cashier (collection) . . . of its sessions how much (money collected) over time how many (sales) over time. What’s next? Transaction–transaction line item #6. “Transaction–Transaction Line Item” Pattern transaction patterns Transaction number date time status aboutMe howMany howMuch rankLineItems calcOverLineItems calcForMe 1-n 1 TransactionLineItem number date time status aboutMe calcForMe rateMe • Typical object interactions howManyOverInterval —> calcForMe calcOverLineItems —> calcForMe howMuchOverInterval —> calcForMe rankLineItems —> rateMe • Examples Transaction: agreement, assignment, authorization, contract, delivery, deposit, incident, inquiry, order, payment, problem, report, purchase, refund, registration, rental, reservation, sale, shift, shipment, subscription, time charge, title, withdrawal. Transaction–transaction line item: deposit–deposit line item; order–order line item; payment–payment line item; rental–rental line item; sale–sale line item; shipment–shipment line item; withdrawal–withdrawal line item. • Combinations participant-transaction; place-transaction; specific item–transaction; transaction–subsequent transaction; transaction line item–subsequent transaction line item; item–line item; specific item–line item. Consider what each transaction object could do, in collaboration with its transaction line items. Continuing, take a look at sale–sale line item: – sale (collection) . . . of its line items calculate subtotal – sale line item (worker) calculate subtotal.
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 55: Applying Patterns: Establish Proble
Page 59 and 60: 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
show all

Connie's Convenience Store - About Peter Coad

Create successful ePaper yourself

Delete template?

Save as template?