Beginning AppleScript®

8.3. Returning Handler Results

Suppose you wanted to write a handler that simply adds two numbers for you. Okay, that's not very practical. Let's assume, however, that you wanted to do it anyway. If you don't want the handler to display or log the result, how can you get that sum as calculated by the handler back to you, the caller? The answer is by using the return command, as you see in the next Try It Out.

8.3.1.

8.3.1.1. Try It Out: Returning Values from Handlers

This program defines a handler called sum that adds two numbers. These two numbers are passed as parameters to the handler. After the numbers have been added together, the handler returns the result.

1. Type the following program into Script Editor:

   -- Illustrate a simple handler to add two numbers and return a value
   
   on sum(x, y)
       return x + y
   end sum
   
   -- test out the handler
   
   log sum(100, 200)
   log sum(100, 200) + sum(300, 400)
   
   set i1 to 100
   set i2 to 50
   log sum(i1, i2/2)

2. Click the Event Log tab and run the program. The following appears in the log:

   (*300*)
   (*1000*)
   (*125*)

8.3.1.2. How It Works

The program begins by defining the sum handler as follows:

on sum(x, y)
    return x + y
end sum

The definition for a handler can appear anywhere in the program, even after it is called. Common programming practice is to place your handler definitions at the beginning of the program where they can be located easily.

The sum handler takes two parameters that you name x and y. Inside the handler, only a single statement appears. This ...