Connie's Convenience Store - About Peter Coad

72 Connie’s Convenience Store Working Out Human-Interaction Dynamics with Scenarios
Responsibilities for reports
Receipt
Establish responsibilities: “what I know.”
Here’s how.
For a report, the “what I know” consists of:
– values, ones that it eventually sends as message arguments.
The “who I know” consists of:
– objects that I can send messages to.
Hence, for a receipt, you need this attribute:
– sale.
Establish responsibilities: “what I do.”
Here’s how.
For a window, the “what I do” are those the report-specific output actions for a window.
Here, it’s:
– generate
which internally invokes:
– add heading lines
– add line item line
– add subtotal line
– add tax line
– add total line
– add payment line.
Add receipt and its responsibilities to the object model (Figure 1–47):
sale
Receipt
generate
addHeadingLines
addPaymentLine
addLineItemLine
addSubtotalLine
addTaxLine
addTotalLine
Figure 1–47: Receipt: “what I know; who I know; what I do.”
WORKING OUT HUMAN-INTERACTION DYNAMICS WITH SCENARIOS
Find meaningful human interaction scenarios
To begin with: where can you find ideas for meaningful scenarios?
Here’s how. Human-interaction scenarios begin with some human interaction.