Sweet UILabel extension for Line Height and Paragraph Height

UILabel+Paragraph.swift

//
//  UILabel+Paragraph.swift  
//
//  Created by Daniel Tavares on 09/02/2016.
//  Copyright © 2016 Daniel Tavares. All rights reserved.
//

import Foundation

//MARK: - Associated Value Struct

//https://wezzard.com/2015/10/09/associated-object-and-swift-struct/
public final class Associated<T>: NSObject, NSCopying {
  public typealias Type = T
  public let value: Type
  
  public init(_ value: Type) { self.value = value }
  
  public func copyWithZone(zone: NSZone) -> AnyObject {
    return self.dynamicType.init(value)
  }
}

extension Associated where T: NSCopying {
  public func copyWithZone(zone: NSZone) -> AnyObject {
    return self.dynamicType.init(value.copyWithZone(zone) as! Type)
  }
}

//MARK: - Line Options Extension

private var LineOptionsKey = "LineOptions"
struct LineOptions {
  let height: CGFloat
  let paragraphHeight: CGFloat
}

@IBDesignable extension UILabel {
  @IBInspectable var lineOptions: LineOptions? {
    get {
      return (objc_getAssociatedObject(self, &LineOptionsKey) as? Associated<LineOptions>).map{$0.value}
    }
    set {
      let value = newValue.map{ Associated<LineOptions>($0) }
      objc_setAssociatedObject(self, &LineOptionsKey, value,.OBJC_ASSOCIATION_RETAIN)
      setText(text, lineOptions: value?.value)
    }
  }
  
  func setText(text: String?, lineOptions: LineOptions?) {
    guard let text = text, lineOptions = lineOptions else { return }
    let paragraphStyle = NSMutableParagraphStyle()
    paragraphStyle.lineSpacing = lineOptions.height
    paragraphStyle.paragraphSpacing = lineOptions.paragraphHeight
    
    let attributedText = NSMutableAttributedString(string: text)
    attributedText.addAttribute(NSParagraphStyleAttributeName, value: paragraphStyle, range: NSMakeRange(0, attributedText.length))
    self.attributedText = attributedText
  }
}

/* - Usage
 let lineOptions = LineOptions(height: 10, paragraphHeight: 16)
 label.setText(description, lineOptions: lineOptions)
*/