SwiftUIを使う際にhex（16進表記）文字列でColorを作成する方法

import Foundation
import SwiftUI

extension Color {
  /// create new object with hex string
  init?(hex: String, opacity: Double = 1.0) {
    // delete "#" prefix
    let hexNorm = hex.hasPrefix("#") ? String(hex.dropFirst(1)) : hex

    // scan each byte of RGB respectively
    let scanner = Scanner(string: hexNorm)
    var color: UInt64 = 0
    if scanner.scanHexInt64(&color) {
      let red = CGFloat((color & 0xFF0000) >> 16) / 255.0
      let green = CGFloat((color & 0x00FF00) >> 8) / 255.0
      let blue = CGFloat(color & 0x0000FF) / 255.0
      self.init(red: red, green: green, blue: blue, opacity: opacity)
    } else {
      // invalid format
      return nil
    }
  }
}

import XCTest
import SwiftUI
@testable import SwiftUIHexColorLib

final class UIColorHexCodeTests: XCTestCase {
  func testWhite() throws {
    let color = Color(hex: "FFFFFF")!
    XCTAssertEqual(color, Color(red: 1.0, green: 1.0, blue: 1.0))
  }

  func testBlack() throws {
    let color = Color(hex: "000000")!
    XCTAssertEqual(color, Color(red: 0.0, green: 0.0, blue: 0.0))
  }

  func testSkyBlue() throws {
    let color = Color(hex: "#3366cc", opacity: 0.9)!
    XCTAssertEqual(color, Color(red: 0.2, green: 0.4, blue: 0.8, opacity: 0.9))
  }

  func testInvalidFormat() throws {
    XCTAssertNil(Color(hex: "white"))
  }
}