1. Mapping Designs to Code
Chapter 20
Mapping Designs to Code
Beware of bugs in the above code. I have only proved it correct, not tried it.
Donald Knuth
CS6359 Fall 2011 John Cole

2. Implementation Model
This is the actual program: source code, database definitions, JSP, ASP, etc.
Code is not part of OOAD, it is the goal
Modern tools permit much design while programming.
CS6359 Fall 2011 John Cole

3. Creativity and Change “Mere coders…”
Your design is a necessary first step, but design models and class diagrams are incomplete
Your understanding of the domain generated during the process provide the basis for writing code (How does this apply to the DB project?)
CS6359 Fall 2011 John Cole

4. Classes from Design Class Diagrams
Some UML tools will generate the basic class structure from your class diagrams
You can easily derive your class in Java, C#, etc from a class diagram
CS6359 Fall 2011 John Cole

5. SalesLineItem Example
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6. Methods from Interaction Diagrams
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7. Methods from Interaction Diagrams
CS6359 Fall 2011 John Cole

8. Collection Classes in Code
One-to-many relationships may require collections.
The text shows:
private List lineItems = new ArrayList();
This is probably better:
private ArrayList<LineItem> lineItems = new ArrayList<LineItem>();
CS6359 Fall 2011 John Cole

9. Exception and Error Handling
This is too often ignored in the design
Consider large-scale strategy
Communication failure
“hard” errors
Consider case-by-case strategy
What if the record we “know” is there is not found
What if there is bad data
In UML, errors can be property strings of messages
CS6359 Fall 2011 John Cole

10. Order of Implementation
From least-coupled to most-coupled (why?)
CS6359 Fall 2011 John Cole

11. Order of Implementation
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12. Test-Driven Development
Create your unit tests before you write the code
Test boundary conditions
CS6359 Fall 2011 John Cole