External Constants for UIColor, UIFont, etc - objective-c

Question

I have a constants.m file that is a centralized collection of many program constants. To set a color, I do this:
#implementation UIColor (UIColor_Constants)
+(UIColor *) defaultResultTableBackgroundColor{
//return [[UIColor colorWithRed:0.6f green:0.004f blue:0.0f alpha:1.0f] retain];
return [[UIColor colorWithRed:0.1f green:0.004f blue:0.3f alpha:0.3f] retain];
}
+(UIColor *) defaultResultHeaderBackgroundColor{
return [[UIColor clearColor] retain];
}
#end
and in the constants.h I have
#interface UIColor (UIColor_Constants)
+(UIColor *) defaultResultTableBackgroundColor;
+(UIColor *) defaultResultHeaderBackgroundColor;
#end
and then just use [UIColor defaultResultTableBackgroundColor] where I want to refer to this constant.
I would like to have some other UIColor and UIFont constants, and, while this works, it seems to be more complicated than it needs to be. Is there an easier way to do this?

Answer 1

I use a constants file for the same purpose. Rather than setting up a whole interface and implementation file, I create the constants file as just the header (.h) file. Then, I define the colors I want to use, such as:
#define globalColor [UIColor colorWithRed:0.1f green:0.004f blue:0.3f alpha:0.3f]
Then, any time you use globalColor it's just like typing in the defined code.

Answer 2

I actually like this way too. One question: why do you retain the uicolor?
This is very dangerous. It's very likely to make a mistake and to create a memory leak.

Answer 3

Here's a great read that explains constants in Objective C:
What is the best way to create constants in Objective-C
Short answer: You're handling this the best way possible.
Macros are not recommended. As some have mentioned, you could #define a macro to handle your colors. That's essentially telling the preprocessor to run find-and-replace on your code. There's a number of downsides to this approach, including scope and type. Apple explicitly recommends against these types of 'constants": https://developer.apple.com/library/mac/documentation/Cocoa/Conceptual/CodingGuidelines/Articles/NamingIvarsAndTypes.html
It's also possible to create a constant:
(in your header, file scope)
extern UIColor * const COLOR_LIGHT_BLUE;
(in your implementation, file scope)
UIColor* const COLOR_LIGHT_BLUE = [[UIColor alloc] initWithRed:21.0f/255 green:180.0f/255 blue:1 alpha:1];
You could, of course, #import this header in your prefix header to save even more typing. Ultimately, though, it's not much of an improvement over what you're already doing.

Answer 4

You create a constant header file which contains all your colors and/or fonts like that:
// Define a convenient macro for example
#define HEXCOLOR(c) [UIColor colorWithRed:((c>>16)&0xFF)/255.0 \
green:((c>>8)&0xFF)/255.0 \
blue:c&0xFF/255.0 \
alpha:0xFF/255.0]
// Then define your constants
#define DefaultResultTableBackgroundColor HEXCOLOR(0x151515)
// etc.

Answer 5

Answer is very simple. It can be used for NSArray and NSDictionary etc.
//Font
static UIFont *titleFont() {
static UIFont *font = nil;
if (!font) {
font = [UIFont systemFontOfSize:25 weight:UIFontWeightHeavy];
}
return font;
}
//Color
static UIColor *prettyPurpleColor() {
static UIColor *color = nil;
if (!color) {
color = [[UIColor purpleColor] colorWithAlphaComponent:0.35];
}
return color;
}