如何通过代码查找iPhone/iPod设备型号(3G,3GS,4,4S)？

#import 

NSString*
machineName()
{
    struct utsname systemInfo;
    uname(&systemInfo);

    return [NSString stringWithCString:systemInfo.machine
                              encoding:NSUTF8StringEncoding];
}

结果应该是:

@"i386"      on the simulator
@"iPod1,1"   on iPod Touch
@"iPod2,1"   on iPod Touch Second Generation
@"iPod3,1"   on iPod Touch Third Generation
@"iPod4,1"   on iPod Touch Fourth Generation
@"iPhone1,1" on iPhone
@"iPhone1,2" on iPhone 3G
@"iPhone2,1" on iPhone 3GS
@"iPad1,1"   on iPad
@"iPad2,1"   on iPad 2
@"iPhone3,1" on iPhone 4
@"iPhone4,1" on iPhone 4S