Sample for view decoration

ViewDecoratorUsingFunctionSample.swift

import UIKit
import PlaygroundSupport

precedencegroup ForwarderApplication {
    associativity: left
}
infix operator |> : ForwarderApplication
func |> <A, B>(x: A, f: (A) -> B) -> B {
    return f(x)
}

precedencegroup ForwarderComposition {
    associativity: left
    higherThan: SingleTypeComposition
}

infix operator >>>: ForwarderComposition
func >>> <A, B, C>(f: @escaping (A) -> B, g: @escaping (B) -> C) -> (A) -> C {
    return { g(f($0)) }
}

precedencegroup SingleTypeComposition {
    associativity: right
    higherThan: ForwarderApplication
}

infix operator <>: SingleTypeComposition
func <> <A>(f: @escaping (A) -> A, g: @escaping (A) -> A) -> (A) -> A {
    return f >>> g
}

func <> <A>(f: @escaping (inout A) -> Void, g: @escaping (inout A) -> Void) -> (inout A) -> Void {
    return { a in
        f(&a)
        g(&a)
    }
}

func <> <A: AnyObject>(f: @escaping (A) -> Void, g: @escaping (A) -> Void) -> (A) -> Void {
    return { a in
        f(a)
        g(a)
    }
}

let cornerRadious: (CGFloat) -> (UIView) -> Void = { radius in
    return { $0.layer.cornerRadius = radius }
}

let shadowRadius: (CGFloat) -> (UIView) -> Void = { radius in
    return {
        $0.layer.shadowRadius = radius
        $0.layer.shadowOpacity = 0.3
        $0.layer.shadowColor = UIColor.black.cgColor
        $0.layer.shadowOffset = CGSize(width: 0, height: radius / 2)
        $0.layer.masksToBounds = false
    }
}

let backgroundColor: (UIColor) -> (UIView) -> Void = { color in
    return { $0.backgroundColor = color }
}

let buttonTitle: (String) -> (UIButton) -> Void = { title in
    return { $0.setTitle(title, for: .normal) }
}

let buttonTitleColor: (UIColor) -> (UIButton) -> Void = { color in
    return { $0.setTitleColor(color, for: .normal) }
}

func borderStyle(color: UIColor, width: CGFloat) -> (UIView) -> Void {
    return {
        $0.layer.borderColor = color.cgColor
        $0.layer.borderWidth = width
    }
}

let baseButtonStyle: (UIButton) -> Void = {
    $0.contentEdgeInsets = UIEdgeInsets(
        top: 12, left: 16, bottom: 12, right: 16)
    $0.titleLabel?.font = .systemFont(ofSize: 16, weight: .medium)
    } <> backgroundColor(.blue)

let baseViewStyle: (UIView) -> Void = {
    $0.backgroundColor = .white
}

let baseTextFieldStyle: (UITextField) -> Void =
    cornerRadious(10)
        <> borderStyle(color: .yellow, width: 3)
        <> { (textField: UITextField) in
            textField.borderStyle = .roundedRect
            textField.heightAnchor.constraint(equalToConstant: 60).isActive = true
}

let textButtonStyle =
    baseButtonStyle
        <> buttonTitleColor(.white)

let okButtonStyle =
    textButtonStyle
        <> cornerRadious(6)
        <> buttonTitle("OK")

let redCardViewStyle =
    baseViewStyle
        <> backgroundColor(.red)
        <> cornerRadious(2)
        <> shadowRadius(4)

let phoneNumberTextFieldStyle =
    baseTextFieldStyle
        <> {
            $0.keyboardType = .numberPad
            $0.placeholder = "電話番号を入力してください"
}


class ViewController: UIViewController {
    
    override func viewDidLoad() {
        super.viewDidLoad()
        self.view.frame = CGRect(x: 0, y: 0, width: 320, height: 480)
        self.view.backgroundColor = .white
        let card = UIView(frame: CGRect(x: 100, y: 100, width: 200, height: 80))
        redCardViewStyle(card)
        self.view.addSubview(card)
        
        let ok = UIButton(frame: CGRect(x: 100, y: 200, width: 100, height: 50))
        okButtonStyle(ok)
        self.view.addSubview(ok)
        
        let input = UITextField(frame: CGRect(x: 50, y: 300, width: 300, height: 50))
        phoneNumberTextFieldStyle(input)
        self.view.addSubview(input)
    }
}

let viewController = ViewController()
PlaygroundPage.current.liveView = viewController