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Editorial Team
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Asked: 2026-06-19T01:11:41+00:00

CGFloat colorR = color.red; It worked for a few builds, but then I modified

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CGFloat colorR = color.red;

It worked for a few builds, but then I modified some code that has nothing to do with color and suddenly that line crashes my app every time I try to run through it, even after undoing those changes.

NSLog(@"%@", color.CGColor);
    //<CGColor %p> [<CGColorSpace %p> (kCGColorSpaceDeviceRGB)] ( 0.2 0.5 0.7 1 )
NSLog(@"%f", color.red);
    //-[UIDeviceRGBColor red]: unrecognized selector sent to instance

Is the availability and (rare) correct function of color.red a bug?

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1 Answer

  1. Editorial Team

    -red is no public instance method for UIColor. UIColors could be represented in any color space and some conversion might be involved. To read the raw RGB components from a UIColor object you must use the method:
    - (BOOL)getRed:(CGFloat *)red green:(CGFloat *)green blue:(CGFloat *)blue alpha:(CGFloat *)alpha

    I don’t know why color.red sometimes works – it could be that certain colors use one of the class cluster instances internally with that method and other times they are stored in another format.

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