AppleScript: The Definitive Guide

Chapter 4. Basic Concepts

This chapter explains how AppleScript works. Its purpose is to provide you with a mental picture of what’s really going on when you use AppleScript. It also acts as a kind of glossary, defining the basic terms and concepts needed for an understanding of AppleScript, but the concepts are presented in an expository order rather than alphabetically.

All subsequent chapters will presuppose some familiarity with the terms and concepts presented in this chapter. You don’t have to grasp everything immediately, and you don’t need to read every section with equal care. But you should at least skim this chapter in order to get your conceptual bearings. You can always come back later and reread a section if you need a refresher on the details.

Apple Event

Apple events lie at the heart of what AppleScript is and why you’re going to use it, and having a sense of what they are will be of tremendous help to you in your AppleScript adventures.

Apple events are the Macintosh’s system-level way of letting one running application communicate with another. Such communication is called interapplication communication . Apple events were introduced in 1991 as part of System 7. I refer to the two parties in an interapplication communication as the sender (the application that sends the message) and the target (the application that receives the message); I find this clearer and more instructive than the more technical terms “client” and “server.”

An Apple event is an astonishingly ...