在新的iOS 11的SDK中，这几个函数参数类型发生了改变，
public func strtod(_: UnsafePointer<Int8>!,_: UnsafeMutablePointer<UnsafeMutablePointer<Int8>?>!) -> Double public func strtof(_: UnsafePointer<Int8>!,_: UnsafeMutablePointer<UnsafeMutablePointer<Int8>?>!) -> Float public func strtol(_ __str: UnsafePointer<Int8>!,_ __endptr: UnsafeMutablePointer<UnsafeMutablePointer<Int8>?>!,_ __base: Int32) -> Int public func strtoll(_ __str: UnsafePointer<Int8>!,_ __base: Int32) -> Int64 /* !__DARWIN_NO_LONG_LONG */ public func strtoul(_ __str: UnsafePointer<Int8>!,_ __base: Int32) -> UInt public func strtoull(_ __str: UnsafePointer<Int8>!,_ __base: Int32) -> UInt64
从原来可以直接传的char*变成了一个UnsafePointer<Int8>。那么我们用到函数的地方也要改变一下，具体代码如下：
let s = hex[hex.characters.index(hex.startIndex,offsetBy: start)..<hex.characters.index(hex.startIndex,offsetBy: end)]
return CGFloat(s.withCString{strtoul($0,nil,16)})
这里的s是一个String类型，他有一个withCString方法。利用这个方法可以将字符串中的字符转换成 UnsafePointer<Int8>类型 原文链接：https://www.f2er.com/swift/320993.html
