Topic: Apple Script

Message

   What is Apple Script?

AppleScript is a scripting
language devised by Apple Computer, and built into Mac OS. More
generally, AppleScript is the word used to designate the Mac OS
scripting interface, which is meant to operate in parallel with the
graphical user interface.

AppleScript was designed to be used primarily as a scripting
language, offering users an intelligent mechanism to control and
exchange information with various applications.

Prior to System 7, the Mac OS application runtime had only a
rudimentary event model that could specify a small and fixed number of
low-level events like "key was pressed" or "mouse was clicked". Each
application was responsible for decoding these low-level events into
meaningful high-level user actions, like "select cut from the Edit
menu". In many cases, the code for reading the event and decoding it
was mixed together; for instance, the code handling a mouse click might
decode it to selecting the Quit item from the File menu, and then quit
the application immediately.

Adding AppleScript support required the author to fully separate
this decoding from carrying out the command, a task Apple referred to
as factoring (...the application). Application developers were
encouraged to write two complete event handling "stacks", one for
handling the low-level events (clicks, etc.), and another for
high-level events (AppleEvents). The actual work code that handled
these commands, once decoded, was to be completely separated and called
identically from both stacks.

AppleScript in Mac OS X

In Mac OS X AppleScript is simpler for developers to implement,
particularly for those applications being developed in Cocoa. Unlike
the Mac OS where events are handled by the applications, under Cocoa,
events are decoded into a "high level" command by the NSApplication
object, and the messages dispatched directly to the correct object.
That is, all Cocoa applications are "factored" by default; the
developer doesn't write any of the event handling code (normally) and
writes only the "work methods" that those events will call.

Another major advantage is that Cocoa objects are presented to the
outside world (other applications and even machines) in a standardized
format that anyone can examine directly. Under Cocoa AppleScript is
much "thinner"; the script engine decodes the script, translates object
names from human-readable to their internal format, and then calls
those methods on the target application directly.

The natural language metaphor

Whereas Apple Events are a way to send messages into applications,
AppleScript is a particular language designed to send Apple Events. In
keeping with the Mac OS tradition of ease-of-use, the AppleScript
language is designed on the natural language metaphor, just as the
graphical user interface is designed on the desktop metaphor.
AppleScript programs are generally readable by anyone, and editable by
most. The language is based largely on HyperCard's HyperTalk language,
extended to refer not only to the HyperCard world of cards and stacks,
but also theoretically to any document. To this end, the AppleScript
team introduced the AppleEvent Object Model (AEOM), which specified the
objects any particular application "knew".

Generally, AEOM defined a number of objects, like "document" or
"paragraph", and the actions that could be done to them, like "cut" and
"close". The system also defined ways to refer to properties of
objects, so one could refer to the "third paragraph of the document
'Good Day'", or the "color of the last word of the front window". AEOM
uses an application dictionary to associate the Apple Events with
human-readable terms, allowing the translation back and forth between
human-readable AppleScript and bytecode Apple Events. To discover what
elements of a program are scriptable, dictionaries for supported
applications may be viewed. (In the Xcode and Script Editor
applications, this is under File → Open Dictionary.)

Examples:

 	  Code: 	
		   tell application "QuarkXPress"

      tell document 1

         tell page 2

            tell text box 1

              set word 5 to "Apple"

             end tell

         end tell

      end tell

  end tell 	

  	  Code: 	
		  pixel 7 of row 3 of TIFF image "my bitmap" 	

AppleScript Studio

With Mac OS X, AppleScript has grown well beyond its humble beginnings. AppleScript Studio is
a development environment, which comes free with Mac OS X, which uses
AppleScript as the primary programming language, in conjunction with
the Cocoa framework used to construct graphical user interfaces.

With Mac OS X v10.3 ("Panther") and Mac OS X v10.4 ("Tiger"),
AppleScript Studio and Project Builder have been rolled into the Xcode
IDE. Interface Builder, another component of Xcode, lets you build a
user interface in a drag-and-drop fashion (similar to Visual Basic) and
then "run" the user interface to see what the forms and menus looks
like.

Panther and Tiger also come with an enhanced version of Script
Editor, the once minimalist editor for compiling and running
AppleScripts. One new feature of this editor is that if you right-click
(or control-click) on the editing area, you get a pop-up menu with a
large range of options for script fragments to paste into your script.
This is an excellent feature for people learning to write AppleScript.
From that menu, you can also open up the directory where these scripts
are kept, and have a look at them. You can also add your own scripts
(although you need to restart Script Editor for these changes to show
up in the pop up menu).


One Stop Testing Forum : Quality Assurance @ OneStopTesting : Software Process Improvement