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copied!<p>You cannot get the address of something returned by a function (or method). You need to get the address of the <code>color</code> ivar directly (i.e. <code>&color</code>). In your case though, I recommend using the approach you proposed yourself (<code>id tempCol = self.color; [NSValue value:&tempCol];</code>).</p> <hr> <p>Note that a method is invoked when using dot notation.</p> <pre><code>self.color // is equal to [self color] </code></pre> <p><code>&([self color])</code> is also impossible because <code>&</code> is resolved at compile-time, not at runtime. The return value of <code>[self color]</code> and <code>self.color</code> (which are equal) aren't yet known at compile-time (even when using <code>@synthesize</code>, since you can change a method's implementation in Objective-C at runtime (e.g. with method swizzling or using categories)).</p> <hr> <p>It seems that you don't fully understand what <code>@synthesize</code> does, so I'll explain. :)</p> <p>Basically what <code>@synthesize</code> does is this: the compiler generates methods and their implementations from the given property names.</p> <p>For example, this property:</p> <pre><code>@property(nonatomic, retain) NSColor *color; </code></pre> <p>Together with this synthesization:</p> <pre><code>@synthesize color; </code></pre> <p>Will insert this code for you in the <code>@implementation</code>:</p> <pre><code>- (NSColor *)color { return color; } - (void)setColor:(NSColor *)newColor { if (color == newColor) { return; } NSColor *theOldColor = color; color = [newColor retain]; [theOldColor release]; } </code></pre> <hr> <p>When you like to use your own setter or getter, you simply define these in the <code>@implementation</code> by using the same method names. You could, for example, return a default color if none is set yet:</p> <pre><code>- (NSColor *)color { if (color) { return color; } return [NSColor whiteColor]; } </code></pre> <p>Now the compiler will generate the setter, but not the getter: it will use the getter you provided, you can still use it with <code>self.color</code>.</p> <hr> <p>You may want to take a look at <a href="http://developer.apple.com/library/mac/#documentation/Cocoa/Conceptual/ObjectiveC/Chapters/ocProperties.html" rel="nofollow">Apple's guide on properties</a>.</p>

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