Building Cocoa Applications: A Step by Step Guide

Building the Calculator’s User Interface

The MainMenu.nib file created by PB and opened in IB above is called, aptly enough, a nib file (nib stands for NeXT Interface Builder — a holdover from the pre-Apple life of this development environment). A nib file stores information about all of the user interface objects in your program, including the windows, controls, and menus; the connections between those objects; and some other objects that IB knows about. When you compile and link the application you are building, the application’s nib file (or files, if the program uses more than one) gets bundled together with the program’s executable code and stored in a package, or app wrapper , folder. This folder has a .app extension and looks like an executable application in the Finder.

The nib files are stored in an undocumented Cocoa proprietary binary format. Fortunately, it doesn’t need to be documented — all of the nib-file management is done by IB. IB is basically a nib editor: when it opens a nib file, it reads the specifications and displays the associated objects. After you make your modifications to the program, IB writes out a new nib file, replacing the old one.

Now that we’ve created the project, we’ll add and customize the windows, panels, and menus needed for our Calculator’s user interface.

Customizing the Main Window

The main window in the Calculator’s interface, currently titled “Window”, doesn’t look anything like a calculator: it’s the wrong shape, it shouldn’t have ...