AppleScript: The Definitive Guide, 2nd Edition

Properties and Elements

The purpose of the chain of ofs and tells is to navigate a structure formed by objects standing in a relationship of owner and attribute to one another. For example, the phrase folder 1 of application "Finder" is needed because folder 1 is an attribute of the Finder, and because I can refer directly to the Finder but not to its attributes. Figuring out how to form a chain of ofs and tells that will let you refer successfully to a desired object constitutes much of the effort of AppleScript programming, as Appendix A vividly illustrates. An application's dictionary is supposed to help you with this, though it often falls short (Chapter 20). AppleScript's own dictionary is not typically visible, so later in the book I'll list the attributes of the built-in datatypes (Chapter 13).

An attribute is either a property or an element . (In fact, I had to coin the term "attribute" because the official AppleScript documentation lacks any comprehensive term for "property or element.") A property is an attribute that this class of object has exactly one of. An element is an attribute that this class of object may have any number of, and in order to refer to one (or more), you have to say which one(s) you mean.

For example, given a list, length is a property; every list has a length, and that's the end of that. But item is an element; a list might not have any items, and if it does have some, it can have any number of them. To speak of an item or items we have to say which ...