UILabelの文字列に線をつけて袋文字にするextension

Playground.swift

// Please, paste the code in playground and execute it.

import UIKit

extension UILabel{

    /// makeOutLine
    ///
    /// - Parameters:
    ///   - strokeWidth: 線の太さ。負数
    ///   - oulineColor: 線の色
    ///   - foregroundColor: 縁取りの中の色
    func makeOutLine(strokeWidth: CGFloat, oulineColor: UIColor, foregroundColor: UIColor) {
        let strokeTextAttributes = [
            .strokeColor : oulineColor,
            .foregroundColor : foregroundColor,
            .strokeWidth : strokeWidth,
            .font : self.font
        ] as [NSAttributedString.Key : Any]
        self.attributedText = NSMutableAttributedString(string: self.text ?? "", attributes: strokeTextAttributes)
    }
}

let label = UILabel(frame: CGRect(x: 0, y: 0, width: 500, height: 60))
label.font = UIFont.boldSystemFont(ofSize: 50)
label.text = "我が家の猫は7.4kg"
label.makeOutLine(strokeWidth: -2.0, oulineColor: .white, foregroundColor: .blue)

UILabelExtensionForOutline.swift

import UIKit

extension UILabel{

    /// makeOutLine
    ///
    /// - Parameters:
    ///   - strokeWidth: 線の太さ。負数
    ///   - oulineColor: 線の色
    ///   - foregroundColor: 縁取りの中の色
    func makeOutLine(strokeWidth: CGFloat, oulineColor: UIColor, foregroundColor: UIColor) {
        let strokeTextAttributes = [
            .strokeColor : oulineColor,
            .foregroundColor : foregroundColor,
            .strokeWidth : strokeWidth,
            .font : self.font
        ] as [NSAttributedString.Key : Any]
        self.attributedText = NSMutableAttributedString(string: self.text ?? "", attributes: strokeTextAttributes)
    }
}