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copied!<p>Most Cocoa projects use underbar as a non-<code>IBOutlet</code> instance variable prefix, and use no prefix for <code>IBOutlet</code> instance variables.</p> <p>The reason I don't use underbars for <code>IBOutlet</code> instance variables is that when a nib file is loaded, if you have a setter method for a connected outlet, that setter will be called. <em>However</em> this mechanism does <em>not</em> use Key-Value Coding, so an IBOutlet whose name is prefixed with an underbar (<em>e.g.</em> <code>_myField</code>) will <em>not</em> be set unless the setter is named exactly like the outlet (<em>e.g.</em> <code>set_myField:</code>), which is non-standard and gross.</p> <p>Also, be aware that using properties like <code>self.myProp</code> is <strong>not</strong> the same as accessing instance variables. You are <strong>sending a message</strong> when you use a property, just like if you used bracket notation like <code>[self myProp]</code>. All properties do is give you a concise syntax for specifying both the getter and setter in a single line, and allow you to synthesize their implementation; they do not actually short-circuit the message dispatch mechanism. If you want to access an instance variable directly but prefix it with <code>self</code> you need to treat <code>self</code> as a pointer, like <code>self->myProp</code> which really is a C-style field access.</p> <p>Finally, never use Hungarian notation when writing Cocoa code, and shy away from other prefixes like "f" and "m_" — that will mark the code as having been written by someone who doesn't "get it" and will cause it to be viewed by suspicion by other Cocoa developers.</p> <p>In general, follow the advice in the <a href="http://developer.apple.com/documentation/Cocoa/Conceptual/CodingGuidelines/index.html" rel="noreferrer" title="Coding Guidelines for Cocoa">Coding Guidelines for Cocoa</a> document at the <a href="http://developer.apple.com/" rel="noreferrer" title="Apple Developer Connection">Apple Developer Connection</a>, and other developers will be able to pick up and understand your code, and your code will work well with all of the Cocoa features that use runtime introspection.</p> <p>Here's what a window controller class might look like, using my conventions:</p> <pre><code>// EmployeeWindowController.h #import <AppKit/NSWindowController.h> @interface EmployeeWindowController : NSWindowController { @private // model object this window is presenting Employee *_employee; // outlets connected to views in the window IBOutlet NSTextField *nameField; IBOutlet NSTextField *titleField; } - (id)initWithEmployee:(Employee *)employee; @property(readwrite, retain) Employee *employee; @end // EmployeeWindowController.m #import "EmployeeWindowController.h" @implementation EmployeeWindowController @synthesize employee = _employee; - (id)initWithEmployee:(Employee *)employee { if (self = [super initWithWindowNibName:@"Employee"]) { _employee = [employee retain]; } return self; } - (void)dealloc { [_employee release]; [super dealloc]; } - (void)windowDidLoad { // populates the window's controls, not necessary if using bindings [nameField setStringValue:self.employee.name]; [titleField setStringValue:self.employee.title]; } @end </code></pre> <p>You'll see that I'm using the instance variable that references an <code>Employee</code> directly in my <code>-init</code> and <code>-dealloc</code> method, while I'm using the property in other methods. That's generally a good pattern with properties: Only ever touch the underlying instance variable for a property in initializers, in <code>-dealloc</code>, and in the getter and setter for the property.</p>

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