如何在代码中判断当前设备是iPhone 4/4S还是iPhone 5？

+ (NSString*)deviceString

{

    // 需要#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;

}