Building Cocoa Applications: A Step by Step Guide

MathDocument Class Modifications

Recall from the last chapter that Cocoa’s multiple-document architecture uses a subclass of the NSDocument class for loading and saving documents, and a subclass of the NSWindowController class for actually managing the document window itself. For simple applications, it may not be necessary to subclass both NSDocument and NSWindowController — you can put all of the necessary code in your subclass of the NSDocument class. However, if you plan to create several different windows for a single document, or if you want to have complex functionality embodied within your document windows, Apple recommends that you subclass NSWindowController. (For a more detailed discussion, we recommend that you read the Cocoa documentation pages for the NSDocument, NSWindowController, and NSDocumentController classes.)

In the next section, we will create a class called PaperController as our subclass of the NSWindowController class. To teach MathDocument about PaperController, we need to make two modifications to the MathDocument.m class file:

1. Back in PB, open the MathDocument.m class file (this is the file that was originally called MyDocument.m).

2. Add the line shown here in bold near the beginning of the MathDocument.m file:

   // MathDocument.m
   
   #import "MathDocument.h"#import "PaperController.h"

Recall that the MathDocument class is a subclass of NSDocument. If we look at the code for MathDocument.m that we listed in the last chapter (or view it in PB), there is a comment ...