WoW:UI best practices: Difference between revisions

WoW:UI best practices (source)

34 bytes removed , 11 September 2008

Anonymous user

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 One stumbling block for Lua programmers coming from other languages is the fact that all variables are global unless specified otherwise. Many times, the use of global variables is necessary: saved variables are created via the global environment; all API functions and UI frames are in the global namespace. However, globals come at a cost of both performance, and naming conflicts.
-Globals in Lua are actually fields in a table called _G. In order to access a global variable, Lua internally translates the variable name to _G["variable name"]. Local variables, on the other hand, are stored on a stack. Stack access is always faster than indexing a table. In code where performance is important (for instance an [[UIHANDLER OnUpdate|OnUpdate handler]]), it's often beneficial to create a local alias to a global function:
+Globals are inefficient to access compared to locals. Whenever a global is accessed, Lua has to call the internal equivalent of getfenv() to figure out where to retrieve the global from. Local variables, on the other hand, are stored on a stack. In code where performance is important (for instance an [[UIHANDLER OnUpdate|OnUpdate handler]]), it's often beneficial to create a local alias to a global function:
   local Foo = Foo
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       DoStuff()
   end
-  if foo[bar] and foo[bar] == 5 then -- will not throw an error
+  if foo and foo[bar] == 5 then -- will not throw an error
       DoStuff()
   end