Beginning AppleScript®

12.2. Script Properties

As previously noted, you can use script objects for various purposes. Many times, you use them to take advantage of the persistent nature of their properties. A property is very similar to a variable. In fact, use of the term property variable is not inaccurate. Like ordinary variables, you can assign values to properties, use them in expressions, pass them as arguments to handlers, and so on.

To define a property, you write the keyword property followed by the name you choose, followed by a colon, followed by the initial value to assign to that property. This is the general format:

property  name : value

This defines a property called name with an initial value specified by value. You must specify an initial value for a property when you define it, whether it's 0, missing value, or the result of an expression.

The following Try It Out illustrates how script properties are initialized once and retain their values through repeated executions of a script.

12.2.1.

12.2.1.1. Try It Out: Working with Script Properties

Follow these steps to work with script properties.

1. Type the following program into Script Editor:

   -- Script properties
   script showXY
       property X : 100
       set Y to 100
       set X to X + 1
       set Y to Y + 1
       log "X = " & (X as string) & ", Y = " & Y as string
   end script
   
   run showXY
   run showXY
   run showXY

2. Click the Event Log tab and run the program. You should see the following output recorded in the Event Log:

   (*X = 101, Y = 101*) (*X = 102, Y = 101*) (*X = 103, ...