12 Step Guide to Lotuscript

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This was given at the Irish Lotus Notes User Group 2010 in Dublin on 1st November 2010

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12 Step Guide to Lotuscript

  1. 1. The 12 step guide toLotusScriptBill Buchanhadsl
  2. 2. 2#1: How to Code• How to code• Code for maintenance• Code updates cost more than new code• Architect well. Get the data model right to start with.• Only code for performance, if required• Get it working before getting it working for speed• Why?• The highest cost in development is software maintenance• Make it easier for the person maintaining the app• It could beYOU
  3. 3. 3#2: How to Test• Test soon, test often, test completely• Look at test-driven development• Write the specification• Write the structure• Write the tests• Write the code• Automatic testing means:• Far easier to regression test all the time• Minimize run-time errors by:• Always assuming that data operations outside thecurrent database may fail• Trapping all run-time errors and providing an executionpath that fails safely
  4. 4. 4#2: How to Test (cont.)• Why test early?• Costs rise as the tests fail further away from development• Cheapest to most expensive are:• Unit tests — by the developer• User acceptance tests (UATs) — by the tester• End-user failure — by the user• The more tests you perform in unit testing:• The cheaper your development will be• The more professional your colleagues will think you are• The more your boss will like you
  5. 5. 5#3: “Measure Twice, Cut Once”• Spend more time thinking and less time coding• Think of at least TWO methods of solving a problem• The best approach is usually a blend of the two• Think about the data model!• Why?• More planning, less work• “You know it’s been a rough nightwhen you wake up next to somecode you don’t recognize.” – Bob Balaban
  6. 6. 6#4: Option Declare• You should always use “Option Declare”• Yes, but why?• If not, all variables are created at run-time as variants• This makes type-checking redundant• Data conversion costs ten times more performance!• And means all errors will be run-time errors• Remember:Test lots, test early• Use the strengths of the compiler to help you• Remember to always declare the type of variables andparameters - otherwise it defaults to variants!
  7. 7. 7#5: The List Operator• List stores a value with a unique lookup key• Pros:• It’s easy and it’s fast• It’s built right into LotusScript, since v4.5• Cons:• You can’t directly read and write a list from a documentitem – convert to an array firstDim Pres list as StringPres(“George”) = “Bush”Pres(“Bill”) = “Clinton”Print “Georges’s last name is: “ + Pres(“George”)if not isElement(Pres(“Chad”)) then print “Chad wasn’tfound”forall thisPres in Pres Print listtag(thisPres) + “ “ + thisPresend forall
  8. 8. 8#6: Defensive Coding• Defensive coding is:• Assume the worst, check all input• On every function• Does this affect performance? Not usually.• A typical function looks like:Function mytest(p1 as String, p2 as String) asinteger mytest = false if p1=”” then exit function if p2=”” then exit function ... Now actually do something! .... mytest = trueend function
  9. 9. 9#7: Extending Arrays the Easy Way• Pros:• No need to keep separate index of array size• Automatically “trims”• Cons:• Slow with large arrays• Need to define some “empty” valueSub initialize() Dim myArray() as String redim myArray(0) call myExtend (myArray, “Hello Sailor”)end subfunction myExtend(S() as String, ns as String) as integerif (S(ubound(S)) <> “”) then redim preserve S(ubound(S)+1)S(ubound(S)) = nsextend = trueend function
  10. 10. • If you have applications with scheduled Agents• Or, if you have a diverse range of clients• Then, you need to log your Agent (both client andscheduled) run-time status• Why?• Applications will break• You need to know when they break• Timing metrics for performance testing• Beware!• Don’t make the loggingso slow that it affectsapplication performance!10#8: Logging
  11. 11. 11#8: Logging (cont.)• OpenLog is an OpenNTF Project:• www.openntf.org• It provides a framework for collecting error logging• To use in your database:• Copy the script libraries from the OpenLog database• Update the code:Function test(param1 as String) as integer Test = false on error goto errorhandler ... Test = trueexitFunction: exit functionerrorhandler: call logError() resume exitfunctionend function
  12. 12. 12#8: Logging (cont.)• Example OpenLog output:
  13. 13. 13#9: Use NotesDateTime Instead of Strings!• Don’t store date/time values as Strings• Use NotesDateTime structures, and save them• Why?• You don’t know how the client will interpret dates• Is it dd/mm/yyyy or mm/dd/yyyy?• It means that views will be able to sort on dates• This happens more often than you think!• And things always break on the 13th of the month
  14. 14. 14#10: Always use full canonical names inreader/author fields!• Common names assume the same hierarchy as theserver in use• Abbreviated names dont work• Always use multi-values for multiple names - sticking ‘;’between names wont work• And always set the field to reader/author inLotusScript!
  15. 15. 15#11: Evaluate• Evaluate allows you to run @Functions withinLotusScript• Sometimes faster, easier• Example: evaluate(|@unique|)• DON’T:• Overuse it. Lots of LotusScript functions mimic @functions• strRight == @StrRight
  16. 16. 16#12: “Trusted Servers”• Scheduled Agents cannot normally open databases onother servers• “Trusted Servers” field in R6 server document, securitysection allows servers to “trust” other servers• This allows you to centralize “collection” Agents• Caveat: Don’t trust servers in another domain!• Pros:• Simplifies architecture• Fewer Agents• Con:• Relies on fast, reliable network infrastructure …
  17. 17. 17#13: LSI_Info()/GetThreadInfo• LSI_INFO() gives some run-time information• Superceded by GetThreadInfo• GetThreadInfo(11) gives calling class• GetThreadInfo(10) gives function name• And lots more• Why?• Error trapping:We can track where we came from• We don’t have to pass lists of parameters to errortrapping code• Prevents “cut-n-paste coding” errors ...
  18. 18. 18#13: LSI_Info()/GetThreadInfo (cont.)Function RaiseError() Dim thisType As String Dim es as String thisType = Typename(Me) Not a class, use the calling module insteadIf (thisType = "") Then thisType = Getthreadinfo(11) es = thisType & "::" & Getthreadinfo(10) & ": " If (Err = 0) Then es = es + "Manually raised an error" Elsees = es + "Run time error: (" + Trim(Str(Err)) + ") " + _ Error$ + " at line: "+ Trim(Str(Erl))End If Print esend function calling code......ExitFunction:exit functionerrorhandler:Call RaiseError()resume exitFunctionend function
  19. 19. 19OkayI added a new step
  20. 20. 20Done!

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