Swift - 从 UIColor 转换为字符串时，UIColor.black 使应用程序崩溃答案

【问题标题】：Swift - UIColor.black crashes app when converting from UIColor to stringSwift - 从 UIColor 转换为字符串时，UIColor.black 使应用程序崩溃
【发布时间】：2019-06-15 12:01:45
【问题描述】：

例如，下面的代码适用于 UIColor.Purple 或 UIColor.Yellow，但是当我使用 UIColor.black 时应用程序崩溃。

致命错误：索引超出范围使用 UIColor.black 时，似乎组件 [2] 和 [3] 不存在。我知道我在强制展开，但不是所有颜色都有 RGBA 吗？

//UIColor RGBA to string
public extension UIColor {

class func StringFromUIColor(color: UIColor) -> String{
    let components = color.cgColor.components
    return "[\(components![0]), \(components![1]), \(components![2]), \(components![3])]"
}

class func UIColorFromString(string: String) -> UIColor {
    let componentsStringStepOne = string.replacingOccurrences(of: "[", with: "")
    let componentsString = componentsStringStepOne.replacingOccurrences(of: "]", with: "")
    let components = componentsString.components(separatedBy: ", ")
    return UIColor(red: CGFloat((components[0] as NSString).floatValue), green: CGFloat((components[1] as NSString).floatValue), blue: CGFloat((components[2] as NSString).floatValue), alpha: CGFloat((components[3] as NSString).floatValue))
}

}

还有没有更好的方法来编写这部分代码？

let componentsStringStepOne = string.replacingOccurrences(of: "[", with: "")
    let componentsString = componentsStringStepOne.replacingOccurrences(of: "]", with: "")
    let components = componentsString.components(separatedBy: ", ")

感谢任何帮助！谢谢。

【问题讨论】：

黑色只有 2 个分量（白色和 alpha）。永远不要假设一种颜色具有特定数量的成分。有不同的颜色模型。白色（灰度）、RGBA、HSBA 等。查询cgColor 有多少组件。
感谢 rmaddy，这解释了错误的原因。

标签： swift uikit uicolor rgba

【解决方案1】：

这是我在 rmaddy 和 kamran 响应之后提出的解决方案。它没有使应用程序崩溃，而且我得到了正确的颜色。它在 plist 中保存了我希望它是黑色还是彩色的外观，例如。 [0.2,0.4,0.5,1.0]。感谢您的帮助

public extension UIColor {

class func StringFromUIColor(color: UIColor) -> String{
    let components = color.cgColor.components
    if components?.count == 2 {
         return "[\(components![0]), \(components![0]), \(components![0]), \(components![1])]"
    } else {
        return "[\(components![0]), \(components![1]), \(components![2]), \(components![3])]"
    }
}

class func UIColorFromString(string: String) -> UIColor {
    let componentsStringStepOne = string.replacingOccurrences(of: "[", with: "")
    let componentsString = componentsStringStepOne.replacingOccurrences(of: "]", with: "")
    let components = componentsString.components(separatedBy: ", ")
    if components.count == 2 {
        return UIColor(white: CGFloat((components[0] as NSString).floatValue), alpha: CGFloat((components[1] as NSString).floatValue))
    } else {
          return UIColor(red: CGFloat((components[0] as NSString).floatValue), green: CGFloat((components[1] as NSString).floatValue), blue: CGFloat((components[2] as NSString).floatValue), alpha: CGFloat((components[3] as NSString).floatValue))
    }
  }
}

【讨论】：