What's the difference between using CGFloat and float?

iphone objective-c cocoa-touch
HelloMoon picture HelloMoon · Aug 12, 2009 · Viewed 101k times · Source

I tend to use CGFloat all over the place, but I wonder if I get a senseless "performance hit" with this. CGFloat seems to be something "heavier" than float, right? At which points should I use CGFloat, and what makes really the difference?

Answer

Quinn Taylor picture Quinn Taylor · Aug 12, 2009

As @weichsel stated, CGFloat is just a typedef for either float or double. You can see for yourself by Command-double-clicking on "CGFloat" in Xcode — it will jump to the CGBase.h header where the typedef is defined. The same approach is used for NSInteger and NSUInteger as well.

These types were introduced to make it easier to write code that works on both 32-bit and 64-bit without modification. However, if all you need is float precision within your own code, you can still use float if you like — it will reduce your memory footprint somewhat. Same goes for integer values.

I suggest you invest the modest time required to make your app 64-bit clean and try running it as such, since most Macs now have 64-bit CPUs and Snow Leopard is fully 64-bit, including the kernel and user applications. Apple's 64-bit Transition Guide for Cocoa is a useful resource.

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