AppleScript: The Definitive Guide, 2nd Edition

Chapter 11. Objects

The purpose of AppleScript is to communicate with scriptable applications. Within the language, these applications present themselves as objects—things to which you send messages, asking for access to their private world of attributes. This metaphor has been extended in AppleScript in a general way (though not, perhaps, with perfect rigor or consistency) to pervade the whole language, so that every value within it is, to a greater or lesser degree, somewhat like a scriptable application. Thus, whether or not AppleScript is an object -oriented language, or even an object-based language, it has a general flavor of involving objects: at every moment in your code, you are talking to something, and most of the things to which you talk have attributes. This chapter is about aspects of the language that involve talking to objects and referring to their attributes.

Messages

The fundamental activity in AppleScript is that of sending messages. Every line of code contains at least one imperative verb. There are actually two kinds of imperative verb: a handler call, which matches a handler definition in your script, and a command , which matches an event defined in a dictionary. The imperative verb is always directed to some specific target , which is supposed to obey it. The medium of communication between the imperative verb in your code and the target that you're talking to is a message .

An object is anything that can be targeted by a message. The most important targets ...