AppleScript: The Definitive Guide

Top-Level Entities

There are three kinds of top-level entity in a script object—properties, handlers, and script objects (see Chapter 7 and Chapter 8 for script properties and handlers).

Accessing Top-Level Entities

Outside a script object, its top-level entities are accessible on demand to any code that can see the script object. This means that they can be both fetched and set by such code.

The syntax is as follows:

• Use the of operator (or the apostrophe-ess operator) to specify the top-level entity in relation to its script object. For example:

  script myScript
          property x : "Howdy"
          on sayHowdy(  )
                  display dialog x
          end sayHowdy
          script innerScript
                  display dialog x
          end script
  end script
  set x of myScript to "Hello"
  myScript's sayHowdy(  ) -- Hello
  run innerScript of myScript -- Hello

• Alternatively, refer to the top-level entity within a tell block addressed to the script object. This requires the use of the keyword its , except in the case of a handler call. For example:

  script myScript
          property x : "Howdy"
          on sayHowdy(  )
                  display dialog x
          end sayHowdy
          script innerScript
                  display dialog x
          end script
  end script
  tell myScript
          set its x to "Hello"
          sayHowdy(  )
          run its innerScript
  end tell

In that last example, if you omit the keyword its from the line where you set x, you set an implicit global x, not the property of myScript. If you omit the keyword its from the line where you run innerScript, there is a runtime error, because no innerScript is in scope.

(It makes no difference whether or ...