Beginning AppleScript®

8.5. Local Variables

So far, you have not set the values of any variables from inside your handlers. However, as you start to write your own handlers, you'll certainly want to do this. Unless specified otherwise, variables to which you assign values inside a handler are called local variables. That means that such variables can only be accessed directly from within the handler in which they appear; their use is local to the handler.

The next Try It Out program is an extension of the preceding Try It Out, "Returning Values from Handlers."

8.5.1.

8.5.1.1. Try It Out: Local Variables

In this program, instead of adding just two numbers, the program takes a list of numbers as its argument, adds them up, and returns the result.

1. Type the following program into Script Editor:

   -- sum all the numbers in a list
   
   on listSum(L)
       set theSum to 0
   
       if class of L is list then
           repeat with num in L
               set theSum to theSum + num
           end repeat
          end
   
       return theSum
   end listSum
   
   -- test out the handler
   
   set myNums to {1, 2, 3, 4, 5}
   
   log listSum(myNums)                    -- 1 + 2 + 3 + 4 + 5
   log listSum(rest of myNums)            -- 2 + 3 + 4 + 5
   log listSum({100, 200, 300, 400, 500}) -- literal list
   
   -- Demonstrate local variable

   set theSum to 999
   listSum (myNums)
   log theSum

2. Click the Event Log tab and run the program. You see the following results in the log:

   (*15*)
   (*14*)
   (*1500*)
   (*999*)

8.5.1.2. How it Works

The definition of the listSum handler is straightforward enough:

on listSum(L) set theSum to 0 if class of L is list then repeat ...