SpacingLabel.swift

//
//  SpacingLabel.swift
//  SpacingLabel
//
//  Created by Viet Nguyen Tran on 6/13/17.
//  Copyright © 2017 iossimple. All rights reserved.
//

import UIKit

@IBDesignable
class SpacingLabel: UILabel {

    @IBInspectable var lineHeight: CGFloat = 0 {
        didSet {
            updateSpacing()
        }
    }
    @IBInspectable var letterSpacing: CGFloat = 0 {
        didSet {
            updateSpacing()
        }
    }
    
    override var text: String? {
        didSet {
            updateSpacing()
        }
    }
    
    func updateSpacing() {
        if let text = self.text, text.characters.count != 0 {
            let attributedString = NSMutableAttributedString(string: text)
            let range = NSMakeRange(0, text.characters.count)
            
            // default attributes
            attributedString.addAttribute(NSFontAttributeName, value: self.font, range: range)
            attributedString.addAttribute(NSForegroundColorAttributeName, value: self.textColor, range: range)
            
            // lineHeight attribute
            if lineHeight != 0 {
                let paragraphStyle = NSMutableParagraphStyle()
                paragraphStyle.minimumLineHeight = lineHeight
                paragraphStyle.maximumLineHeight = lineHeight
                paragraphStyle.alignment = self.textAlignment // alignment from UILabel
                attributedString.addAttribute(NSParagraphStyleAttributeName, value: paragraphStyle, range: range)
            }
            // letter Spacing
            if letterSpacing != 0 {
                attributedString.addAttribute(NSKernAttributeName, value: letterSpacing, range: range)
            }
            
            // show label
            self.attributedText = attributedString
        } else {
            self.attributedText = nil
        }
    }
}