Learning Cocoa with Objective-C, 2nd Edition

Chapter 10. Multiple Document Architecture

So far, our examples have centered on applications that have a single GUI. However, in reality many of the applications we use day-in and day-out—such as word processors and web browsers—are based around the idea of a document. They provide a framework for viewing or generating identically-contained, but uniquely-composed, sets of data that can be stored in files.

A document-based application must perform the following tasks:

• Create new documents

• Open existing documents stored in files

• Save documents to user-designated files and locations

• Revert to previously saved documents

• Close documents, usually after prompting the user to save changes

• Print documents and allow the page layout to be modified

• Monitor and set the document’s edited status, as well as reflect that status to the user

• Manage document windows, including setting window titles

Cocoa provides a multiple-document architecture, helping you take care of these tasks easily. Using this architecture drastically simplifies the work developers must do to implement a multidocument application. Once you understand how this architecture works, you can have a multidocument application up and running in minutes.

This chapter begins with an overview of Cocoa’s multiple-document architecture and then presents an in-depth look at the classes that make up this architecture. The final part of the chapter guides you through the process of creating a simple multiple-document text-editing application. ...