Name

run handler

Syntax

on run
 (* do major scripting here *)
end run

Description

Whether you like it or not, most of your scripts contain a run handler implicitly or invisibly. What Apple Computer calls an “implicit run handler” involves all the statements in a script except for property definitions, subroutine definitions, and any script objects (see Chapter 9). This means that all of these statements are enclosed in an invisible on run...end run subroutine block. This implicit run handler is called each time:

• The applet icon is double-clicked.

• The user chooses the applet from the Apple menu.

• The user chooses the applet from the Apple Menu Items folder.

• The applet is placed in startup disk:System Folder:Startup Items and the computer is restarted.

You can explicitly code the run handler to clarify to readers of your code exactly what happens when the applet receives a run command, as in the next example. If this script did not include the on run...end run statements, then its implicit run handler would still encompass the statements:

add(  )

and:

display dialog "I received a run command " & howmany & " times"

The applet property howmany increments by 1 each time this applet receives a run command:

property howmany : 0
on run
   add(  )
   display dialog "I received a run command " & howmany & " times"
end run

on add(  )
   set howmany to howmany + 1
end add

Tip

Sending a run command to an application, as in tell app "Photoshop 5.5" to run, loads the application if it is not already running. Use activate to gain the focus of the application (i.e., highlight the program on the desktop) when it is already running. Sending a run command to an AppleScript causes its implicit or explicit run handler to execute.