Smart Swift Initialisation

init.swift

class Foo {

    // Keep default values for optionals anyway since we can do shorter self.init calls
    // when the call is unambiguous from the convenience init
    private init(image: UIImage? = nil, images: [UIImage]? = nil, imageURL: NSURL? = nil, blurStyle: UIBlurEffectStyle = .Dark) {
        // init
    }
    
    // By exposing convenience initialisers that take mutually exclusive parameters
    // we remove the need to do any kind of assertion on them
    
    public convenience init(image: UIImage, blurStyle: UIBlurEffectStyle = .Dark) {
        self.init(image: image, images: nil, blurStyle: blurStyle)
    }
    
    public convenience init(images: [UIImage], blurStyle: UIBlurEffectStyle = .Dark) {
        self.init(image: nil, images: images, blurStyle: blurStyle)
    }
    
    public convenience init(imageURL: NSURL, blurStyle: UIBlurEffectStyle = .Dark) {
        // No need to set images to nil here since this call is unambiguous
        self.init(image: nil, imageURL: imageURL, blurStyle: blurStyle)
    }

}

let foo1 = Foo(UIImage(named: "fun")!)
let foo2 = Foo([UIImage(…)!, UIImage(…)!], blurStyle: .Light) 
let foo3 = Foo(NSURL(string: …)!)