Wiley-World.of.Warcraft.Programming.A.Guide.and.Reference.for.Creating.WoW.Addons

Appendix A ■ Best Practices 1321Use Tables as a Logic StructureSometimes you will have a long chain of if ... elseif where each clausecompares the same variable to some constant. The prime example in addonprogramming is an OnEvent script. Consider the following:if event == “SOME_EVENT“ then-- do stuffelseif event == “ANOTHER_EVENT“ then-- do stuffelseif event == “THIRD_EVENT“ then-- do stuffelseif event == “FOURTH_EVENT“ then-- do stuffendYou can use a table in a manner similar to the ‘‘Rework Repetitive Code’’section earlier in this appendix. Instead of the if statement, you fill a tablewith functions indexed by the name of the event:local eventHandlers = {[“SOME_EVENT“] = function(frame, namedArgument)-- do stuffend,[“ANOTHER_EVENT“] = function(frame, namedArgument1, namedArgument2)-- do stuffend,[“THIRD_EVENT“] = function(frame)-- do stuffend,[“FOURTH_EVENT“] = function()-- do stuffend}Now the OnEvent script can be simplified to four lines (or one if you arecareful about what events you register):function MyEventHandler(frame, event, ...)local handler = eventHandlers[event]if handler thenhandler(frame, ...)endendThis technique affords a few advantages:The underlying architecture of the table lookup usually executes morequickly than a string of if ... elseif clauses, especially with a largenumber of entries.