Saving UIColor to and loading from NSUserDefaults

I've got the answer by myself

Save

const CGFloat  *components = CGColorGetComponents(pColor.CGColor);
NSUserDefaults *prefs = [NSUserDefaults standardUserDefaults];
[prefs setFloat:components[0]  forKey:@"cr"];
[prefs setFloat:components[1]  forKey:@"cg"];
[prefs setFloat:components[2]  forKey:@"cb"];
[prefs setFloat:components[3]  forKey:@"ca"];

Load

NSUserDefaults *prefs = [NSUserDefaults standardUserDefaults];
UIColor* tColor = [UIColor colorWithRed:[prefs floatForKey:@"cr"] green:[prefs floatForKey:@"cg"] blue:[prefs floatForKey:@"cb"] alpha:[prefs floatForKey:@"ca"]];

One way of doing it might be to archive it (like with NSColor, though I haven't tested this):

NSData *colorData = [NSKeyedArchiver archivedDataWithRootObject:color];
[[NSUserDefaults standardUserDefaults] setObject:colorData forKey:@"myColor"];

And to get it back:

NSData *colorData = [[NSUserDefaults standardUserDefaults] objectForKey:@"myColor"];
UIColor *color = [NSKeyedUnarchiver unarchiveObjectWithData:colorData];

With the accepted answer, you'll quickly end up with a lot of NSKeyed archives & unarchives all over your code. A cleaner solution is to extend UserDefaults. This is exactly what extensions are for; UserDefaults probably doesn't know about UIColor as it is because UIKit and Foundation are different frameworks.

Swift

extension UserDefaults {

    func color(forKey key: String) -> UIColor? {
        var color: UIColor?
        if let colorData = data(forKey: key) {
            color = NSKeyedUnarchiver.unarchiveObject(with: colorData) as? UIColor
        }
        return color
    }

    func set(_ value: UIColor?, forKey key: String) {
        var colorData: Data?
        if let color = value {
            colorData = NSKeyedArchiver.archivedData(withRootObject: color)
        }
        set(colorData, forKey: key)
    }

}

Swift 4.2

extension UserDefaults {

    func color(forKey key: String) -> UIColor? {

        guard let colorData = data(forKey: key) else { return nil }

        do {
            return try NSKeyedUnarchiver.unarchivedObject(ofClass: UIColor.self, from: colorData)
        } catch let error {
            print("color error \(error.localizedDescription)")
            return nil
        }

    }

    func set(_ value: UIColor?, forKey key: String) {

        guard let color = value else { return }
        do {
            let data = try NSKeyedArchiver.archivedData(withRootObject: color, requiringSecureCoding: false)
            set(data, forKey: key)
        } catch let error {
            print("error color key data not saved \(error.localizedDescription)")
        }

    }

}

Usage

UserDefaults.standard.set(UIColor.white, forKey: "white")
let whiteColor = UserDefaults.standard.color(forKey: "white")

This can also be done in Objective-C with a category.

I've added the Swift file as a gist here.

Thanks for Erica's UIColor category. I did not really like saving 4 floats in the preferences, and just wanted a single entry.

So using Erica's UIColor category, I was able to convert the RGB color to/from an NSString which can be saved in the preferences.

// Save a color
NSString *theColorStr = [self.artistColor stringFromColor];
[[NSUserDefaults standardUserDefaults] setObject:theColorStr forKey:@"myColor"];

// Read a color
NSString *theColorStr = [[NSUserDefaults standardUserDefaults] objectForKey:@"myColor"];
if ([theColorStr length] > 0) {
    self.myColor = [UIColor colorWithString:theColorStr];
} else {
    self.myColor = [UIColor colorWithRed:88.0/255.0 green:151.0/255.0 blue:237.0/255.0 alpha:1.0];
}