How do I comfortably use CGColor in an NSArray with CGGradient

问题

I have two UIColor instances and want to use them creating a gradient. The code works, but it gives me a warning when I call the arrayWithObject: constructor:

warning: Semantic Issue: Incompatible pointer types sending 'CGColorRef' (aka 'struct CGColor *') to parameter of type 'id'

I suspect there lurks other issues related to the warning (leaks for instance). Here is the snippet:

   UIColor *startColor, *endColor; 
   // ...
   NSArray *colors = [NSArray arrayWithObjects:
                      startColor.CGColor, endColor.CGColor, nil];
   CGGradientRef gradient = CGGradientCreateWithColors(colorSpace, 
                     (CFArrayRef) colors, NULL);

How can I rewrite the code to get rid of this warning in a safe way ?

• I tried creating a CGArrayRef manually, but that got a bit nasty after a while.
• CGGradientCreateWithColorComponents works, but I don't like having to manually merge all color components into an CGFloat components[]

回答1:

Try this

UIColor *startColor, *endColor; 
   // ...
   NSArray *colors = [NSArray arrayWithObjects:
                      (id)startColor.CGColor, (id)endColor.CGColor, nil];
   CGGradientRef gradient = CGGradientCreateWithColors(colorSpace, 
                     (CFArrayRef) colors, NULL);

来源：https://stackoverflow.com/questions/5948237/how-do-i-comfortably-use-cgcolor-in-an-nsarray-with-cggradient