Is Macro Better Than UIColor for Setting RGB Color

问题:

I have this macro in my header file:

#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]

And I am using this as something like this in my .m file:

cell.textColor = UIColorFromRGB(0x663333);

So I want to ask everyone is this better or should I use this approach:

cell.textColor = [UIColor colorWithRed:66/255.0
                                 green:33/255.0
                                  blue:33/255.0
                                 alpha:1.0];

Which one is the better approach?

回答1:

A middle ground might be your best option. You could define either a regular C or objective-C function to do what your macro is doing now:

// As a C function:
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];
}

// As an Objective-C function:
- (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];
}

If you decide to stick with the macro, though, you should put parentheses around rgbValue wherever it appears. If I decide to call your macro with:

UIColorFromRGB(0xFF0000 + 0x00CC00 + 0x000099);

you may run into trouble.

The last bit of code is certainly the most readable, but probably the least portable - you can't call it simply from anywhere in your program.

All in all, I'd suggest refactoring your macro into a function and leaving it at that.

回答2:

or create a separate category, so you only need to import one .h file:

@interface UIColor (util)
+ (UIColor *) colorWithHexString:(NSString *)hex;
+ (UIColor *) colorWithHexValue: (NSInteger) hex;
@end

and

#import "UIColor-util.h"

@implementation UIColor (util)

// Create a color using a string with a webcolor
// ex. [UIColor colorWithHexString:@"#03047F"]
+ (UIColor *) colorWithHexString:(NSString *)hexstr {
    NSScanner *scanner;
    unsigned int rgbval;

    scanner = [NSScanner scannerWithString: hexstr];
    [scanner setCharactersToBeSkipped:[NSCharacterSet characterSetWithCharactersInString:@"#"]];
    [scanner scanHexInt: &rgbval];

    return [UIColor colorWithHexValue: rgbval];
}

// Create a color using a hex RGB value
// ex. [UIColor colorWithHexValue: 0x03047F]
+ (UIColor *) colorWithHexValue: (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];

}


@end

回答3:

How about creating your own:

#define RGB(r, g, b) \
    [UIColor colorWithRed:(r)/255.0 green:(g)/255.0 blue:(b)/255.0 alpha:1]
#define RGBA(r, g, b, a) \
    [UIColor colorWithRed:(r)/255.0 green:(g)/255.0 blue:(b)/255.0 alpha:(a)]

Then use it:

cell.textColor = RGB(0x66, 0x33, 0x33);

Seems simple enough to use, uses hex values for colors and without needing additional calculation overhead.

回答4:

I typically recommend functions rather than complex #defines. If inlining has a real benefit, the compiler will generally do it for you. #defines make debugging difficult, particularly when they're complex (and this one is).

But there's nothing wrong with using a function here. The only nitpick I'd say is that you should be using CGFloat rather than float, but there's nothing wrong with the hex notation if it's more comfortable for you. If you have a lot of these, I can see where using Web color notation may be convenient. But avoid macros.

回答5:

I.m.h.o the UIcolor method is more readable. I think macro's are great if they solve a problem; i.e. provide more performance and/or readable code.

It is not clear to me what the advantage of using a macro is in this case, so I'd prefer the second option.

回答6:

Keep in mind that 33 != 0x33. The first is decimal notation and the second is hexadecimal. They're both valid, but they are different. Your second option should read

cell.textColor = [UIColor colorWithRed:0x66/255.0
                             green:0x33/255.0
                              blue:0x33/255.0
                             alpha:1.0];

or

cell.textColor = [UIColor colorWithRed:102/255.0
                             green:51/255.0
                              blue:51/255.0
                             alpha:1.0];

回答7:

Nice Marius, but to compile I had to get rid of the parenthesis, as follows (otherwise, Objective C takes it literally and you get a syntax compilation error:

#define RGB(r,g,b) [UIColor colorWithRed:r/255.0 green:g/255.0 blue:b/255.0 alpha:1.0]
...

NSArray *palette;
...

palette = [NSArray arrayWithObjects:
             RGB(0,0,0),
             RGB(255,0,0), // red
...