Making a function globally available in Objective-C - objective-c

Question

In previous project I had this function defined in AppDeligate.m and it was globally available to all the parts of the app:
#define UIColorFromRGB(rgbValue) [UIColor \
colorWithRed:((float)((rgbValue & 0xFF0000) >> 16))/255.0 \
green:((float)((rgbValue & 0xFF00) >> 8))/255.0 \
blue:((float)(rgbValue & 0xFF))/255.0 alpha:1.0]
Now for some reason when I place this code in a new project, only the specific class can see the function, but the child classes do not see it.
How do I make this function globally available?

Answer 1

You can define your macro in the .pch file of your project, but it's generally a bad idea, since it will produce code which is difficult to read, maintain and debug.
In your specific case I'd rather create a category on UIColor.
Here's a implementation with extra stuff which may come in handy.
UIColor+Extra.h
#import <UIKit/UIKit.h>
#interface UIColor (Extra)
+ (instancetype)extra_colorWith255BasedRed:(NSUInteger)red green:(NSUInteger)green blue:(NSUInteger)blue;
+ (instancetype)extra_colorWith255BasedRed:(NSUInteger)red green:(NSUInteger)green blue:(NSUInteger)blue alpha:(CGFloat)alpha;
+ (instancetype)extra_colorWithHex:(NSInteger)hex;
#end
UIColor+Extra.m
#import "UIColor+Extra.h"
#implementation UIColor (Extra)
+ (instancetype)extra_colorWith255BasedRed:(NSUInteger)red green:(NSUInteger)green blue:(NSUInteger)blue {
return [self colorWith255BasedRed:red green:green blue:blue alpha:1.0];
}
+ (instancetype)extra_colorWith255BasedRed:(NSUInteger)red green:(NSUInteger)green blue:(NSUInteger)blue alpha:(CGFloat)alpha {
return [self colorWithRed:red/255.0f green:green/255.0f blue:blue/255.0f alpha:alpha];
}
+ (instancetype)extra_colorWithHex:(NSInteger)hex {
return [UIColor colorWith255BasedRed:((hex & 0xFF0000) >> 16) green:((hex & 0xFF00) >> 8) blue:(hex & 0xFF)];
}
#end
Then just place
#import "UIColor+Extra.h"
in your .pch file and use it elsewhere.
Examples
UIColor * cyan = [UIColor extra_colorWithHex:0x00FFFF];
UIColor * magenta = [UIColor extra_colorWith255BasedRed:255 green:0 blue:255];

Answer 2

If you add the file to YOURPROJECTNAME-Prefix.pch, it will be added as a precompiled header, and available in all your code-files.

Answer 3

Audun Kjelstrup has the best answer.
You also have the option to setup a static method inside a class.
+ (UIColor *)UIColorFromRGB {}

Answer 4

I agree with Gabriele about macros (undesirable as functions) and that what you are trying to do would be nice/appropriate in a category. However, I also want to point out that Objective-C can also do C-style functions (as opposed to the macro that you have shown).
For example:
// Header
UIColor * UIColorFromRGB(NSInteger rgbValue);
// Implementation
UIColor * UIColorFromRGB(NSInteger rgbValue)
{
return [UIColor colorWithRed: ((float)((rgbValue & 0xFF0000) >> 16))/255.0
green: ((float)((rgbValue & 0xFF00) >> 8))/255.0 \
blue: ((float)(rgbValue & 0xFF))/255.0 alpha:1.0];
}