ViewController.swift

 //
//  ViewController.swift
//  FunctionalComposedControllerSample
//
//  Created by freddi on 2020/10/16.
//

import UIKit

infix operator |>

func |> <A: AnyObject>(v: A, f: @escaping (A) -> Void) -> A {
    f(v)
    return v
}

precedencegroup ApplyOperator {
    associativity: left
}

public func |> <A, B>(_ lhs: A, _ rhs: @escaping (A) -> B) -> B {
    return rhs(lhs)
}

infix operator <>

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

func modifyColor(color: UIColor) -> (UIButton) -> () {
    return { button in
        button.backgroundColor = color
    }
}

func modifyAsAccountInfoButton(button: UIButton) {
    button.layer.cornerRadius = 20
    button.clipsToBounds = true
    button.setTitleColor(.white, for: .normal)
}

let normalLoginStyle = modifyColor(color: .green) <> modifyAsAccountInfoButton
let logoutStyle = modifyColor(color: .red) <> modifyAsAccountInfoButton
let twitterStyle = modifyColor(color: .blue) <> modifyAsAccountInfoButton

class ViewController: UIViewController {

    let loginButton = UIButton() |> (normalLoginStyle)
    let logoutButton = UIButton() |> (logoutStyle)
    let loginWithTwitterButton = UIButton() |> (twitterStyle)

    override func viewDidLoad() {
        super.viewDidLoad()
        // Add button's to view ...
    }
}