External constants for UIColor, UIFont, etc.

Question

I have a constants.m file, which is a centralized set of many program constants. To set the 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 constants. 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 although this works, it seems more complicated than it should be. Is there an easier way to do this?

Answer 1

I also like this way. One question: why do you keep uicolor? It is very dangerous. This can lead to an error and create a memory leak.

Answer 2

I use a constant file for the same purpose. Instead of customizing the entire interface and implementation file, I create a constant file as a header (.h) file. Then I define the colors that I want to use, for example:

 #define globalColor [UIColor colorWithRed:0.1f green:0.004f blue:0.3f alpha:0.3f] 

Then, whenever you use globalColor , it is just like input to a specific code.

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 do this best.

Macros are not recommended. As already mentioned, you can #define a macro to process your colors. This essentially tells the preprocessor to run find-and-replace in your code. There are a number of disadvantages to this approach, including volume and type. Apple explicitly recommends against these types of "constants": https://developer.apple.com/library/mac/documentation/Cocoa/Conceptual/CodingGuidelines/Articles/NamingIvarsAndTypes.html

It is also possible to create a constant:

(in your title, content area)

 extern UIColor * const COLOR_LIGHT_BLUE; 

(in your implementation, 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 the prefix header to save even more input. Ultimately, this does not greatly improve what you are already doing.

Answer 4

You create a file with a permanent header that contains all your colors and / or such fonts:

 // 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

The 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; }