I'd like to create a CAGradientLayer Subclass/Utility class - ios

Question

I've been programming in one way or another for 30+ years, but I'm new to Swift and iOS programming and working on my first app. I've worked out how to create a CAGradientLayer to show a gradient on screen, but I'd like to create a utility class/extension/subclass with some predefined gradients in it.
I am assuming I can do this by creating subclasses of CAGradientLayer with the properties pre-set at initialisation time, but I'm not sure of the correct syntax to do this. I guess I am missing some basic Swift requirements?
I've tried the following:
let greenBlueGradient = GreenBlueGradient.greenBlueGradient()
class GreenBlueGradient: CAGradientLayer {
override init() {
super.init()
}
func greenBlueGradient() -> GreenBlueGradient {
self.colors = [ UIColor.init( red: 0.05, green: 0.75, blue: 0.91, alpha: 1.0 ).CGColor, UIColor.init( red: 0.56, green: 0.93, blue: 0.56, alpha: 1.0 ).CGColor ]
return self
}
required init?(coder aDecoder: NSCoder) {
super.init(coder: aDecoder)
}
}
But I'm getting the error "Missing argument for parameter #1 in call" on the let line. What am I missing? Surely there is a more efficient way of doing this? I sort of have in my head that I will be able to create some sort of utility class/extension that will return a CAGradientLayer with the colors already set ready for me to set the frame and insert it into my view hierarchy.

Answer 1

You shoud add an extension of CAGradientLayer in other file for exemple :
in file "UIExtensionsCAGradientLayer.swift"
extension CAGradientLayer {
func setupGreenBlurGradient(){
self.colors = [UIColor.init( red: 0.05,
green: 0.75,
blue: 0.91,
alpha: 1.0).CGColor,
UIColor.init( red: 0.56,
green: 0.93,
blue: 0.56,
alpha: 1.0 ).CGColor ]
}
}
Then in the file where you need the green blur gradient you do :
let greenGradientBlur = CAGradientLayer(layer : layer)
greenGradientBlur.setupGreenBlueGradient()

Answer 2

The error message here is a bit misleading. (File a bug about that. Or fix it yourself, if you're so inclined, now that Swift is open source.)
Your attempt to call GreenBlueGradient.greenBlueGradient() fails because you're calling an instance method as if it were a class method. That call would succeed if you'd declared greenBlueGradient() as a class func. However, that function's implementation relies on self.
What you probably want instead is to add your customization to init:
override init() {
super.init()
self.colors = [
UIColor(red: 0.05, green: 0.75, blue: 0.91, alpha: 1.0).CGColor,
UIColor(red: 0.56, green: 0.93, blue: 0.56, alpha: 1.0).CGColor,
]
}
That way, a client can get your custom gradient just by constructing an instance:
let greenBlueGradient = GreenBlueGradient()
Pretty colors, by the way.