SpacingButton.swift

//
//  SpacingButton.swift
//  MglabSpice
//
//  Created by Viet Nguyen Tran on 6/14/17.
//  Copyright © 2017 iossimple. All rights reserved.
//

import UIKit

@IBDesignable
class SpacingButton: UIButton {
    @IBInspectable var letterSpacing: CGFloat = 0 {
        didSet {
            updateSpacing()
        }
    }

    override func setTitle(_ title: String?, for state: UIControlState) {
        super.setTitle(title, for: state)
        updateSpacing()
    }
    
    func updateSpacing() {
        if let text = self.title(for: .normal), text.characters.count != 0 {
            let attributedString = NSMutableAttributedString(string: text)
            let range = NSMakeRange(0, text.characters.count)
            
            // default attributes
            if let font = self.titleLabel?.font  {
                attributedString.addAttribute(NSFontAttributeName, value: font, range: range)
            }
            if let color = self.titleColor(for: .normal) {
                attributedString.addAttribute(NSForegroundColorAttributeName, value: color, range: range)
            }
            
            // letter Spacing
            if letterSpacing != 0 {
                let letterSpacingRange = NSMakeRange(range.location, range.length - 1)
                attributedString.addAttribute(NSKernAttributeName, value: letterSpacing, range: letterSpacingRange)
            }
            
            // show text on button
            self.setAttributedTitle(attributedString, for: .normal)
        } else {
            self.setAttributedTitle(nil, for: .normal)
        }
    }
}