Adds a border to the UIButton

UIButton+Border.swift

//  Created by Evgeny Konkin on 17/04/2020.

import UIKit

enum BorderSide {
    case top, bottom, left, right
}

extension UIButton {
    
    /// Добавляем границу кнопки
    func addBorder(side: BorderSide, color: UIColor, thickness: CGFloat) {
        
        let border = CALayer()
        border.backgroundColor = color.cgColor
        
        switch side {
        case .top:
            border.frame = CGRect(x: 0, y: 0, width: frame.size.width, height: thickness)
        case .bottom:
            border.frame = CGRect(x: 0, y: frame.size.height - thickness, width: frame.size.width, height: thickness)
        case .left:
            border.frame = CGRect(x: 0, y: 0, width: thickness, height: frame.size.height)
        case .right:
            border.frame = CGRect(x: frame.size.width, y: 0, width: thickness, height: frame.size.height)
        }
        
        self.layer.addSublayer(border)
    }
}

// Usage

let button = UIButton()
button.addBorder(side: .bottom, color: .gray, thickness: 0.5)

//