在Swift和count元素中将十六进制颜色转换为RGB

Question

我看到一些答案说在这行上使用countElements或count，但我在我的代码中得到错误:

if (count(cString) != 6) {

说"不能用String类型的参数列表调用count "

我已经尝试了一些其他的想法，但没有找到正确的解决方案，有什么想法吗?

完整功能如下:

func colorWithHexString (hex:String) -> UIColor {
    var cString:String = hex.stringByTrimmingCharactersInSet(NSCharacterSet.whitespaceAndNewlineCharacterSet()).uppercaseString
    if (cString.hasPrefix("#")) {
        cString = (cString as NSString).substringFromIndex(1)
    }
    if (count(cString) != 6) {
        return UIColor.grayColor()
    }
    var rString = (cString as NSString).substringToIndex(2)
    var gString = ((cString as NSString).substringFromIndex(2) as NSString).substringToIndex(2)
    var bString = ((cString as NSString).substringFromIndex(4) as NSString).substringToIndex(2)
    var r:CUnsignedInt = 0, g:CUnsignedInt = 0, b:CUnsignedInt = 0;
    NSScanner(string: rString).scanHexInt(&r)
    NSScanner(string: gString).scanHexInt(&g)
    NSScanner(string: bString).scanHexInt(&b)

    return UIColor(red: CGFloat(r) / 255.0, green: CGFloat(g) / 255.0, blue: CGFloat(b) / 255.0, alpha: CGFloat(1))
}

Answer 1

试试cString.characters.count。

Apple在Swift 2中更新了String，使其不再符合count所定义的CollectionType协议。取而代之的是，Swift字符串现在通过characters属性公开一个字符集合。

这是因为字符串不一定表现得像其他集合——例如，如果你向数组中添加一个数字，你期望该数组的计数增加，但是向字符串中添加某些unicode字符——例如重音，则可能不会增加字符串的长度

详情见https://developer.apple.com/swift/blog/?id=30

修改后的方法是:

func colorWithHexString (hex:String) -> UIColor {
 var cString:String = hex.stringByTrimmingCharactersInSet(NSCharacterSet.whitespaceAndNewlineCharacterSet()).uppercaseString
  if (cString.hasPrefix("#")) {
    cString = (cString as NSString).substringFromIndex(1)
  }
  if (cString.characters.count != 6) {
    return UIColor.grayColor()
  }
  let rString = (cString as NSString).substringToIndex(2)
  let gString = ((cString as NSString).substringFromIndex(2) as NSString).substringToIndex(2)
  let bString = ((cString as NSString).substringFromIndex(4) as NSString).substringToIndex(2)
  var r:CUnsignedInt = 0, g:CUnsignedInt = 0, b:CUnsignedInt = 0;
  NSScanner(string: rString).scanHexInt(&r)
  NSScanner(string: gString).scanHexInt(&g)
  NSScanner(string: bString).scanHexInt(&b)

  return UIColor(red: CGFloat(r) / 255.0, green: CGFloat(g) / 255.0, blue: CGFloat(b) / 255.0, alpha: CGFloat(1))
}

注意一些vars已经变成了let s，因为它们从未发生过突变