Swift Extension Not working

Question

I've added an extension to UIColor for some colors that I use throughout my app. Here's an example:

extension UIColor {
    func appLightGrayColor() -> UIColor {
    return UIColor(red: 190.0/255.0, green: 190.0/255.0, blue: 190.0/255.0, alpha: 1.0)
    }

    func grayScaleColor(grayScale : CGFloat) -> UIColor {
    return UIColor(red: grayScale/255.0, green: grayScale/255.0, blue: grayScale/255.0, alpha: 1.0)
    }
}

However, when I try to call it, the only way that I've been able to compile without errors is this:

UINavigationBar.appearance().barTintColor = UIColor.appLightGrayColor(UIColor())()

Here's what I get with autocomplete:

What am I doing wrong?

Santo

Answer 1

While Bryan's answer is still correct, with the release of Swift 3, the preferred "Swifty" way of doing things has changed a bit.

With Swift 3, predefined UIColors are used accordingly:

var myColor: UIColor = .white // or .clear or whatever

Therefore, if you want something similar, such as the following...

var myColor: UIColor = .myCustomColor

...then, you would define the extension like so:

extension UIColor
    {
    public class var myCustomColor: UIColor
        {
        return UIColor(red: 248/255, green: 248/255, blue: 248/255, alpha: 1.0)
        }
    }

In fact, Apple defines white as:

public class var white: UIColor

Stavros

Talking about the "Swifty" way of doing things... Shouldn't opening braces be on the same line as the statement? :) – Lucerne

Don't get me started on that! It will only become a religious war. :-) – Stavros

haha I know I know - everyone has their way :P I follow something similar to github.com/raywenderlich/swift-style-guide – Lucerne

Answer 2

You have added instance method, but what you really want is class method

extension UIColor {
    class func appLightGrayColor() -> UIColor {
    return UIColor(red: 190.0/255.0, green: 190.0/255.0, blue: 190.0/255.0, alpha: 1.0)
    }

    class func grayScaleColor(grayScale : CGFloat) -> UIColor {
    return UIColor(red: grayScale/255.0, green: grayScale/255.0, blue: grayScale/255.0, alpha: 1.0)
    }
}

Arabeila

+1, also, I suggest that appLightGrayColor() -> UIColor { return UIColor.grayScaleColor(190.0) } – Acinus