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Inside Macintosh: Interapplication Communication /

Chapter 1 - Introduction to Interapplication Communication / Sending and Responding to Apple Events

Standard Apple Events

The current edition of Apple Event Registry: Standard Suites defines the standard suites of Apple events, which are groups of related events that are usually implemented together. The Apple Event Registrar maintains the Apple Event Registry: Standard Suites and other information about the ongoing development of Apple event suites.

The standard suites include the following:

• The Required suite consists of the four Apple events that the Finder sends to applications. These events are Open Application, Open Documents, Print Documents, and Quit Application. The Finder uses the required events as part of the mechanisms in System 7 and later versions for launching and terminating applications. To support System 7, your application must support the required Apple events as described in the chapter "Responding to Apple Events" in this book.
• The Core suite consists of the basic Apple events, including Get Data, Set Data, Move, Delete, and Save, that nearly all applications use to communicate. You should support the Apple events in the Core suite that make sense for your application.
• A functional-area suite consists of a group of Apple events that support a related functional area. Functional-area suites include the Text suite and the Database suite. You can decide which functional-area suites to support according to which features your application provides. For example, most word-processing applications should support the Text suite, and most database applications should support the Database suite.

You do not need to implement all Apple events at once. You should begin by supporting the required Apple events, then add support for the events sent by the Edition Manager, the core events, and the functional-area events as appropriate for your application.

If necessary, you can extend the definitions of the standard Apple events to suit specific capabilities of your application. You can also define your own custom Apple events. However, only those applications that choose to support your custom Apple events explicitly will be able to make use of them. If all applications communicated solely by means of custom Apple events, every application would have to support all other applications' custom events. Instead of creating custom Apple events, try to use the standard Apple events and extend their definitions as necessary.

Apple events describe actions to be performed by the applications that receive them. In addition to a vocabulary of actions, or "verbs," effective communication between applications requires a method of referring to windows, data (such as words or graphic elements), files, folders, volumes, zones, and other items on which actions can be performed. The Apple Event Manager provides a method for specifying structured names, or "noun phrases," that applications can use to describe the objects on which Apple events act.

The Apple Event Registry: Standard Suites includes definitions for Apple event object classes, which are simply names for objects that can be acted upon by each kind of Apple event. Applications use these definitions and Apple Event Manager routines to create complex descriptions of almost any discrete item in another application or its documents. For example, an application could use Apple Event Manager routines and standard object class definitions to construct a Get Data event that requests "the most recent invoice to John Chapman in the Invoices database on the Archives server in the Accounting zone" and send the event to the appropriate application across the network.

An Apple event object is any item supported by an application, such as a word, paragraph, shape, or document, that can be described in an Apple event. In the example just given, the specified invoice, the Invoices database, the Archives server, and the Accounting zone are nested Apple event objects. Nearly any item that a user can differentiate and manipulate on a Macintosh computer can be described as an Apple event object of a specified object class nested within other Apple event objects. When handling an Apple event that includes such a description, an application must locate the specified Apple event object and perform the requested action on it.

Most of the standard Apple events defined in the Apple Event Registry: Standard Suites require your application to recognize specific Apple event object classes. Support for the standard Apple events, including Apple event object classes, allows your application to respond to requests for services or information from any other application or process.