‘substring（from :)’不推荐使用：请使用字符串切片下标和’partial range from’运算符。 Swift 4错误

我正在将我现有的应用程序从Swift 3转换为Swift 4 。 它给出了错误：

‘substring（from :)’不推荐使用：请使用字符串切片下标和’partial range from’运算符。

和

‘characters’已弃用：请直接使用String或Substring

我的Swift 3代码是：

 public convenience init?(hexString: String, alpha: Float) { var hex = hexString // Check for hash and remove the hash if hex.hasPrefix("#") { hex = hex.substring(from: hex.characters.index(hex.startIndex, offsetBy: 1)) } if (hex.range(of: "(^[0-9A-Fa-f]{6}$)|(^[0-9A-Fa-f]{3}$)", options: .regularExpression) != nil) { // Deal with 3 character Hex strings if hex.characters.count == 3 { let redHex = hex.substring(to: hex.characters.index(hex.startIndex, offsetBy: 1)) let greenHex = hex.substring(with: (hex.characters.index(hex.startIndex, offsetBy: 1) ..< hex.characters.index(hex.startIndex, offsetBy: 2))) let blueHex = hex.substring(from: hex.characters.index(hex.startIndex, offsetBy: 2)) hex = redHex + redHex + greenHex + greenHex + blueHex + blueHex } let redHex = hex.substring(to: hex.characters.index(hex.startIndex, offsetBy: 2)) let greenHex = hex.substring(with: (hex.characters.index(hex.startIndex, offsetBy: 2) ..< hex.characters.index(hex.startIndex, offsetBy: 4))) let blueHex = hex.substring(with: (hex.characters.index(hex.startIndex, offsetBy: 4) ..< hex.characters.index(hex.startIndex, offsetBy: 6))) var redInt: CUnsignedInt = 0 var greenInt: CUnsignedInt = 0 var blueInt: CUnsignedInt = 0 Scanner(string: redHex).scanHexInt32(&redInt) Scanner(string: greenHex).scanHexInt32(&greenInt) Scanner(string: blueHex).scanHexInt32(&blueInt) self.init(red: CGFloat(redInt) / 255.0, green: CGFloat(greenInt) / 255.0, blue: CGFloat(blueInt) / 255.0, alpha: CGFloat(alpha)) } else { self.init() return nil } } 

如何将其转换为Swift 4 ？

Answer 1

‘characters’已弃用：请直接使用String或Substring

为此，您可以直接在swift 4中循环遍历字符串，因此不需要字符数组。

并为

‘substring（from :)’不推荐使用：请使用字符串切片下标和’partial range from’运算符。

请参阅如何在Swift 4中使用字符串切片下标？