Diamond Operator: reusability and styling

DiamondOperator.swift

import UIKit
import PlaygroundSupport

precedencegroup SingleTypeComposition {
    associativity: right
}

infix operator <>: SingleTypeComposition

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

let backgroundColor = UIColor.lightGray
let borderColor = UIColor.gray

enum FontSize: CGFloat {
    case big = 30.0
    case normal = 20
    case small = 15
    case tiny = 12
}


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


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

let styleViewCircleBase: (UIView) -> Void =
    styleViewBackground(color: backgroundColor)
        <> {
            $0.layer.cornerRadius = $0.frame.width * 0.5
            $0.layer.masksToBounds = true
        }

let styleViewCircleBorder: (UIView) -> Void =
    styleViewCircleBase
        <> styleViewBorder(color: borderColor, width: 4)

let styleLabelBase: (UILabel) -> Void = {
    $0.textAlignment = .center
    $0.textColor = .white
    $0.numberOfLines = 0
}

let styleLabelBigFont: (UILabel) -> Void = {
    $0.font = UIFont.systemFont(ofSize: FontSize.big.rawValue, weight: .bold)
}

let styleLabelCircle: (UILabel) -> Void =
    styleLabelBase
    <> styleViewCircleBorder
    <> styleLabelBigFont

let styleLabelCheckMark: (UILabel) -> Void =
    styleLabelCircle
        <> {
            $0.text = "√"
        }

let view = UIView(frame: CGRect(x: 0, y: 0, width: 400, height: 800))
view.backgroundColor = .white

let borderCircle = UIView(frame: CGRect(x: 50, y: 50, width: 100, height: 100))
styleViewCircleBorder(borderCircle)
view.addSubview(borderCircle)


let label = UILabel(frame: CGRect(x: 50, y: 170, width: 80, height: 80))
label.text = "B"
styleLabelCircle(label)
view.addSubview(label)


let checkLabel = UILabel(frame: CGRect(x: 50, y: 290, width: 200, height: 200))
styleLabelCheckMark(checkLabel)
view.addSubview(checkLabel)


PlaygroundPage.current.liveView = view