AppleScript programming in Objective-C

Create QR Code in Objective-C AppleScript programming

folder (you need root privileges to add items to this folder). To see what services are available from a scripting addition, open the Script Editor and select File Open Dictionary. Select the scripting addition from the list and click the Open button.

Compared to other languages, AppleScript looks more like English than code. In general, AppleScript is a dynamically typed, English-like scripting language that supports many of the features of standard UNIX scripting languages but is geared to the Macintosh and is primarily used for application automation and control. As such, it s stronger in these areas than as a general-purpose programming language. AppleScripts consist of a series of statements. You structure these statements as commands that operate on objects. A command is an AppleScript statement that requests an action of an object. Objects are either application objects or system objects. Application objects are associated with a particular application, covering the services to which the application will respond. System objects are associated with the Mac OS X system. You manipulate objects with structured or procedural code. In AppleScript, you can view application programs as object hierarchies. For example, an application s object hierarchy is laid out in its dictionary, which is viewable from the Script Editor. Figure 7.4 shows the dictionary for TextEdit. The left window lists the application s commands and objects; commands are in plain text, and objects are italicized. Commands operate on objects. For example, the command open operates on objects such as a window or document. Conceptually, this is similar to object-oriented

Figure 7.4 The dictionary for TextEdit lists the application s commands and objects; commands appear in plain text and objects in italic text.

programming, where you send a message to an object that performs the appropriate action. In AppleScript, you scope commands and objects using the tell statement:2

Data types and data structures AppleScript supports the usual data types, such as the integer, real (float), string, and boolean, as well as structured types such as Date, List, and Record. Because the language is dynamically (loosely) typed, you do not need to specify the type of a variable at development time. Table 7.1 shows the syntax and an example of the most commonly used data types.

Table 7.1 Type Integer Real Number Boolean String Text Date List AppleScript data types and examples Description Unsigned, nonfractional number Unsigned, fractional number Either an Integer or a Real Logical value, true or false Series of 1-byte characters Same as String String that holds a date Collection of values, which can be of any data type (array) Example

(see Integer and Real examples)

string"

(see String example)

set now to date "5/22/02" Set aList to {x, y, z, 1, "as"} -- get the first items in the list2 item 1 of aList Set js-bach to {name: "JS-Bach", period:"Baroque", birth:1685, death:1750} -- get Bach's birth date birth of js-bach

Collection of properties (hash)

If you like, you can explicitly specify a type of a variable as follows:

The List data type is an array, which enables you to hold data of different types. Unlike in C, Lists begin at index one, not zero. In addition, you can nest Lists within Lists:

set aList to {n, x, aBool, msgStr, date} set aNewList to {aList, {1, 2, 3, 4}}

The following script demonstrates how to perform some simple math operations in AppleScript:

set total to 0 set aList to {1, 2, 3, 4, 5, 6, 7, 8, 12, 45, 67, 54, 12, 4, 12, 12, 45, 56} repeat with n in aList set total to total + n end repeat set mean to total div (length of aList) -- log is not the mathematical log, but rather a log, -- or print statement. log "length of list: " & (length of aList) log "sum of list: " & total log "mean of list: " & mean

In addition to these data types, AppleScript defines many constants such as pi, true, false, space, return, and tab. See the AppleScript documents for a complete list of these constants. In figure 7.5, you can see the output of the previous script. (log is useful for performing printf-style debugging of a script. To see the output of a log command, open Controls Open Event Log and make sure you enable Show Events and Show Event Results.) Control and iteration statements Control statements affect the execution path through a script. AppleScript supports the usual assortment of control and iteration statements found in other languages, including if, else if, repeat, and exit. if and else if The if and else if control statements are used to define which statements are executed based on some condition. Table 7.2 lists some examples.