Xcode 8 Beta 4 CGColor.components unavailable

Question

Whilst the code below worked previously, it has stopped working in Xcode 8 Beta 4, presumably because the components return was a very un-Swift-y C-array of floats,

Answer 1

This looks like a transitional beta issue.

The Swift repo on Github includes an extensive SDK overlay for CoreGraphics, including a new version of CGColor.components whose return type is a Swift array instead of an UnsafePointer. Part of how they make that SDK overlay work is API notes, which map some of the underlying C calls to double-underscore'd Swift methods so that the overlay can wrap them in a more-Swifty interface.

It looks like the beta 4 and beta 5 compilers picked up the API notes change, but not the overlay that includes the new version of components. Presumably a future beta (or the final Swift 3.0 / Xcode 8.0 release) will include everything that's now on github.

Answer 2

I may be mistaking something, but you can find this in the imported header of CGColor.

/* Return the color components (including alpha) associated with `color'. */

@available(OSX 10.3, *)
public var __unsafeComponents: UnsafePointer<CGFloat>? { get }

Isn't this what you are looking for?

I can write something like this:

public var cgColour: CGColor {
    get {
        return CGColor(red: self.colourRed, green: self.colourGreen, blue: self.colourBlue, alpha: self.colourAlpha)
    }
    set {
        if let comps = newValue.__unsafeComponents, newValue.numberOfComponents == 4 {
            self.colourRed = comps[0]
            self.colourGreen = comps[1]
            self.colourBlue = comps[2]
            self.colourAlpha = comps[3]
        }
    }
}

It works as I expect, but I'm not sure it's as you expect, or Apple would treat this as using a private API. (Apple's latest documentation of CGColor does not contain double-underscore leaded symbols.)

Answer 3

extension UIColor {
    var all4Components:(red:CGFloat, green:CGFloat, blue: CGFloat, alpha:CGFloat) {
    let components = self.cgColor.components!
    let red = components[0]
    let green = components[1]
    let blue = components[2]
    let alpha = components[3]
    return (red:red, green:green, blue: blue, alpha:alpha)

    }
}

Answer 4

I'm also a little perplexed as to why they have removed the components property from CGColor, as there doesn't seem to be any kind of obvious replacement method/property. It looks like they're trying to get people to use the higher level UIColor or NSColor classes instead. (As @rickster has discovered, this looks more like a simple transitional issue).

One solution, as you're working with RGB colors, would be to simply wrap your CGColor in a UIColor/NSColor, and then use the getRed(_:green:blue:alpha:) method to get out the components instead.

public var cgColour : CGColor {
    get {
        return CGColor(red: colourRed, green: colourGreen, blue: colourBlue, alpha: colourAlpha)
    }
    set {
        NSColor(cgColor: newValue)?.getRed(&colourRed, green: &colourGreen, blue: &colourBlue, alpha: &colourAlpha)
    }
}

Perhaps not the most ideal solution – would certainly be interested to know if anyone else has a better one, or knows more about this change. Depending on the usage of this property, you may also want to consider simply making it of type UIColor/NSColor to prevent the needless wrapping that this solution requires.

Answer 5

@Hamish's answer works, but my original intent was not to use UIColor or NSColor so that my code works in both iOS & MacOS. @LeoDabus suggested using SKColor, but that's just a type alias to either NSColor or UIColor, and doesn't have a direct init from CGColor anyway, however, Leo's suggestion prompted me to refine my kludge using CIColor instead:

import CoreImage

extension CGColor {
    var components: (red: CGFloat, green: CGFloat, blue: CGFloat, alpha: CGFloat) {
        let ciColor = CIColor(cgColor: self)
        return (ciColor.red, ciColor.green, ciColor.blue, ciColor.alpha)
    }
}