Reusable Styler

Styler.swift

//: Playground - noun: a place where people can play

import UIKit

class Styler<ViewType: UIView> {

    private let styler: (ViewType) -> Void

    init(_ styler: @escaping (ViewType) -> Void) {
        self.styler = styler
    }

    func apply(on view: ViewType) {
        styler(view)
    }

}

extension Styler where ViewType: UIView {

    static var blueBackground: Styler {
        return Styler {
            $0.backgroundColor = .blue
        }
    }

}

extension Styler where ViewType: UIButton {

    static var defaultText: Styler {
        return Styler {
            // Call other "parent" styles
            Styler.blueBackground.apply(on: $0)

            $0.setTitle("defaultText", for: .normal)
        }
    }

    static var blue: Styler {
        return Styler {
            $0.backgroundColor = .blue
        }
    }

}

extension UIButton {

    // TODO: How to generalize this accross all UIViews?
    func apply(_ styler: Styler<UIButton>) {
        styler.apply(on: self)
    }

}

let button = UIButton(type: .custom)

button.apply(.defaultText)

button.titleLabel?.text
button.backgroundColor