使用Objective-C建立UUID

轉自: http://blog.prosight.me/index.php/2010/11/670

UUID是128位的值，它可以保證唯一性。通常，它是由機器本身網卡的MAC地址和當前系統時間來產生的。

UUID是由中劃線串連而成的字串。例如：13222F23-C76A-7781-0C12-0293E3B34398.

下面這個方法可以產生UUID並以字串的方式進行返回。

- (NSString *)createUUID
{
// Create universally unique identifier (object)
  CFUUIDRef uuidObject = CFUUIDCreate(kCFAllocatorDefault);

// Get the string representation of CFUUID object.
  NSString *uuidStr = (NSString *)CFUUIDCreateString(kCFAllocatorDefault, uuidObject);

// If needed, here is how to get a representation in bytes, returned as a structure
// typedef struct {
//   UInt8 byte0;
//   UInt8 byte1;
//   …
//   UInt8 byte15;
// } CFUUIDBytes;
  CFUUIDBytes bytes = CFUUIDGetUUIDBytes(uuidObject);

  CFRelease(uuidObject);

return uuidStr;
}