How to automatically choose between NSColor and UIColor for the correct build system? (Using a #define, or something)

Question

I'm trying to make a NSObject subclass that will have a lot of methods that return colors, so I wanna return UIColor if I'm building for iOS or NSColor if I'm building for OS X.
This is kind of a pseudo-code of what the expected behaviour should be:

#define COLOR #if TARGET_OS_IPHONE UIColor #elif TARGET_OS_MAC NSColor #endif

+ (COLOR *)makeMeColorful;

Is it possible to do something like this instead of making 2 methods for each of my object's method (one for iOS and another for OS X)?

Chasechaser

See #15323609 – Windermere

Answer 1

This is absolutely doable. SKColor from SpriteKit for example, is defined like:

#if TARGET_OS_IPHONE
#define SKColor UIColor
#else
#define SKColor NSColor
#endif

And then utilized like this:

SKColor *color = [SKColor colorWithHue:0.5 saturation:1.0 brightness:1.0 alpha:1.0];

This simply takes advantage of the fact that UIColor and NSColor share some of their class methods.

Evan

Very clever Apple. ;) – Appassionato

Note that NSColor and UIColor don't share all their API, though, so you have to be careful not to call methods that exist only on one or the other. – Zollie

Answer 2

If you are using Swift try something in the lines of

#if os(macOS)
    typealias Color = NSColor
#else
    typealias Color = UIColor
#endif

Works for macOS, iOS, tvOS and watchOS. More on Swift's preprocessor directives.

Boehmenist

Swift doesn't use flags like TARGET_OS_IPHONE. But it does have target-platform conditionals like #if os(iOS). – Zollie

Answer 3

You can use a typedef within the preprocessor conditional:

#if TARGET_OS_IPHONE
typedef UIColor MONPlatformColor;
#elif
typedef NSColor MONPlatformColor;
#endif

And your API would be declared:

+ (MONPlatformColor *)makeMeColorful;

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