Humans are ill-equiped to model complex worlds, data structures, and processes in memory (as we must do everyday while we are programming). Fortunately for us, several generations of hackers and computer scientists have developed practices to improve software quality, increase code reuse, and improve programmer efficiency. In this session, I review the most relevant of those practices and the way those ideas can be applied to improve programming in FileMaker Pro.

1. FileMaker Developer Conference 2010
Session COR010
Small Things | Loosely Joined
Lessons Learned to Improve Quality,
Reuse Code, and Program Efficiently)
Dr. Don Levan
Vanguard Custom Software

2. Who am I?
• President, Vanguard Custom Software
• FileMaker 7, 8, 9, 10 Certified Developer
• Licensed Clinical Psychologist
• Former Photojournalist
• Founder of the “Craft of FileMaker” Seminar Series
2

3. Please See the handout (on the CD):
vanguardcs.net/devcon
You will find:
Summary of the
problem
Key points
References
Information about the
“Craft of FileMaker”
Seminar Series

4. A Story about Craft.

5. Programming is hard.

8. Small Things | Loosely Joined

9. Small Things | Loosely Joined
Fail Loudly

10. Small Things | Loosely Joined
Fail Loudly
Fold Knowledge into Data

11. Case Study: Tekserve’s Payment Routines
(With Technical Debt)

12. Small Things | Loosely Joined

13. Small Things:
Are compact, transparent, and do one thing well.

14. Small Things:
Are compact, transparent, and do one thing well.

15. Small Things:
Are compact, transparent, and do one thing well.

16. DECREASING TRANSPARENCY: BY NESTING IFS

17. INCREASING TRANSPARENCY: BY REFACTORING

18. DECREASING TRANSPARENCY: BY EXITING LATE

19. INCREASING TRANSPARENCY: BY REFACTORING

20. INCREASING TRANSPARENCY: BY NAMING WELL
Field Names:
Lowercase and underscore.
No punctuation other than underscore. No Periods.
No spaces.
Boolean: Use a form of the verb “to be” or “to have”,
such as “is_customer” or “has_children”.
Example: first_name
Tekserve FileMaker & MySQL Conventions (2009)

21. INCREASING TRANSPARENCY: BY NAMING WELL
Variable Names:
Use a name that clearly communicates intent.
Follow the convention for field names.
Example: $report_type
Tekserve FileMaker & MySQL Conventions (2009)

22. INCREASING TRANSPARENCY: BY NAMING WELL
Script Names:
Name scripts to describe their purpose.
Use active voice.
Add a parenthesis to indicate any parameters.
Example: Process payment ( entry; type; action)
Tekserve FileMaker & MySQL Conventions (2009)

23. SMALL THINGS: DO ONE THING WELL
The Unix Pipe: $ program_1 | program_2 | program_3

24. SMALL THINGS: DO ONE THING WELL
The Unix Pipe: $ history | grep “ssh -p”

25. Loosely Joined programs:
“Keep it dry, shy,
and tell the other
guy.”
Andy Hunt and Dave Thomas, IEEE Software 2000

26. LOOSELY JOINED PROGRAMS:
Do not repeat themselves (Dry).
Keep their variables as local as possible (Shy).
Break complex scripts into disconnected layers.
Pass in the data (Tell the other guy).
Expect the output of any script to be used by another.

27. LOOSELY JOINED PROGRAMS: UNIX PIPES
All Unix programs have multiple streams of information:
Standard Input
Standard Output
Standard Error
The pipe connects the Standard Output of one program
to the Standard input of another.

28. LOOSELY JOINED PROGRAMS: FILEMAKER PIPES
Unix FileMaker
Standard Input Get (ScriptParameter)
Standard Output Get (ScriptResult)
Standard Error Get (ScriptResult)

29. LOOSELY JOINED PROGRAMS: FILEMAKER PIPES
Main Script ( param_1; param_2)
Set up variables
Sub-Script ( param_1 )
Perform Script (pass parameters)
Return error & output
Set Variables to error and output
Sub-Script ( param_1 )
Perform Script (pass parameters)
Return error & output
Set Variables to error and output
Exit Script
(Return error & output)

30. Small Things | Loosely Joined
Case Study: Tekserve’s Payment Routines
(Re-factored)

31. Small Things | Loosely Joined

32. Small Things | Loosely Joined
Fail Loudly

33. Fail Loudly, and as soon as possible.

34. or,
“Dead scripts tell no
lies.”
The Pragmatic Programmer, From Journeyman to Master

35. Suppressing Errors

36. Capturing Errors

37. Dealing with Errors

38. Returning Errors

39. Logging Errors

40. Logging Errors

41. Logging Errors

42. Logging Errors

43. Small Things | Loosely Joined
Fail Loudly

44. Small Things | Loosely Joined
Fail Loudly
Fold Knowledge into Data

45. Fold Knowledge into Data
so program logic can be stupid and robust.

46. FOLD KNOWLEDGE INTO DATA
Differentiate between data and program logic.
Separate the data out into script parameters, custom
functions, and table records.
Use SetFieldByname, Evaluate, and other functions to
simplify script logic.

47. Fold Knowledge into Data
Case Study: Creating child portal records.

48. Fold Knowledge into Data
Case Study: Creating flexible reports

49. Fold Knowledge into Data
Case Study: Synchronizing FileMaker and MySQL

50. Small Things | Loosely Joined
Fail Loudly
Fold Knowledge into Data

51. Small Things | Loosely Joined
Fail Loudly
Fold Knowledge into Data

52. Small Things | Loosely Joined
Fail Loudly
Fold Knowledge into Data

53. “The only way to write complex software that won’t
fall on its face is to hold its global complexity down –
build it out of simple parts connected by well-defined
interfaces, so that most problems are local and you
can have some hope of upgrading a part without
breaking the whole.”
The art of Unix Programming (p. 14)

54. FileMaker Developer Conference 2010
Web Update Page
www.filemaker.com/devcon/speaker_updates
(This is also listed in your conference binder)
This session WILL / WILL NOT
have updates.

55. Thank You!
Please remember to fill out your
evaluation at: www.filemaker.com/
devcon/evaluations