Values and Constants

Values are data that can be represented, stored, and manipulated in scripts. AppleScript recognizes many types of values, including character strings, real numbers, integers, lists, and dates. Values are different from application objects, which can also be manipulated from AppleScript but are contained in applications or their documents. Objects are described in Objects and References.

Each value belongs to a value class , which is a category of values that are represented in the same way and respond to the same operators. To find out how to represent a particular value, or which operators it responds to, check its value class definition. AppleScript can coerce a value of one class into a value of another. The possible coercions depend on the class of the original value.

This chapter describes how to interpret value class definitions, discusses the common characteristics of all value classes, and presents definitions of many value classes supported in AppleScript. It also describes how to coerce values and describes various types of constant values you can use in scripts.

Value classes and coercions are described in the following sections:

Common Value Class Definitions provides detailed definitions for a set of commonly used AppleScript value classes. Each class is described in a separate section. The sections follow the format described in Using Value Class Definitions.
Unicode Text and International Text describes two string value classes that you use mainly to transfer data between applications.
Unit Type Value Classes provides an overview of the value classes you use to work with measurements of length, area, cubic and liquid volume, mass, and temperature.
Coercing Values describes how AppleScript coerces values. It provides a table that shows the available coercions for common value classes.

A constant is a reserved word with a predefined value. You can use constants to supply values in scripts. Constants are described in the following sections:

Constant describes the value class Constant.
Constants describes the different kinds of constants used with AppleScript.