In the code, how can I determine whether the current device is iPhone 4/4S or iPhone 5?

+ ( NSString *)deviceString {      // # Import "sys/utsname. H"      struct  utsname systemInfo;      uname(&systemInfo);      NSString  *deviceString = [ NSString  stringWithCString:systemInfo.machine encoding: NSUTF8StringEncoding ];            if  ([deviceString isEqualToString:@ "iPhone1,1" ])     return  @ "iPhone 1G" ;      if  ([deviceString isEqualToString:@ "iPhone1,2" ])     return  @ "iPhone 3G" ;      if  ([deviceString isEqualToString:@ "iPhone2,1" ])     return  @ "iPhone 3GS" ;      if  ([deviceString isEqualToString:@ "iPhone3,1" ])     return  @ "iPhone 4" ;      if  ([deviceString isEqualToString:@ "iPhone4,1" ])     return  @ "iPhone 4S" ;      if  ([deviceString isEqualToString:@ "iPhone5,2" ])     return  @ "iPhone 5" ;      if  ([deviceString isEqualToString:@ "iPhone3,2" ])     return  @ "Verizon iPhone 4" ;      if  ([deviceString isEqualToString:@ "iPod1,1" ])       return  @ "iPod Touch 1G" ;      if  ([deviceString isEqualToString:@ "iPod2,1" ])       return  @ "iPod Touch 2G" ;      if  ([deviceString isEqualToString:@ "iPod3,1" ])       return  @ "iPod Touch 3G" ;      if  ([deviceString isEqualToString:@ "iPod4,1" ])       return  @ "iPod Touch 4G" ;      if  ([deviceString isEqualToString:@ "iPad1,1" ])       return  @ "iPad" ;      if  ([deviceString isEqualToString:@ "iPad2,1" ])       return  @ "iPad 2 (WiFi)" ;      if  ([deviceString isEqualToString:@ "iPad2,2" ])       return  @ "iPad 2 (GSM)" ;      if  ([deviceString isEqualToString:@ "iPad2,3" ])       return  @ "iPad 2 (CDMA)" ;      if  ([deviceString isEqualToString:@ "i386" ])          return  @ "Simulator" ;      if  ([deviceString isEqualToString:@ "x86_64" ])        return  @ "Simulator" ;      NSLog (@ "NOTE: Unknown device type: %@" , deviceString);      return  deviceString; }

In the code, how can I determine whether the current device is iPhone 4/4S or iPhone 5?