可以从 UIDevice 的属性 model 得到在现在执行的环境。例子如下：

NSString *modelname = [[UIDevice currentDevice]model];
if ([modelname isEqualToString:@"iPhone"]) {
  // iPhone
}
if ([modelname isEqualToString:@"IPod Touch"]) {
  // iPod touch
}
if ([modelname isEqualToString:@"iPhone Simulator"]) {
  // iPhone Simulator
}

 也可以通过宏定义区分 

#if TARGET_OS_IPHONE
    // iPhone Device
#endif

#if TARGET_IPHONE_SIMULATOR
    // iPhone Simulator
#endif

#if !TARGET_IPHONE_SIMULATOR
    // iPhone Device
#endif

 ios设备版本的区分-iphone3gs,iphone4.... 

ios提供了几种c函数来获得相应信息如下

struct utsname u;
uname(&u); ///-----get device struct info
NSString *machine = [NSString stringWithCString:u.machine];

if ([machine isEqualToString:@"iPhone1,1"]) {
  // iPhone 1G
}
if ([machine isEqualToString:@"iPhone1,2"]) {
  // iPhone 3G
}
if ([machine isEqualToString:@"iPhone2,1"]) {
  // iPhone 3GS
}
if ([machine isEqualToString:@"iPod1,1"]) {
  // iPod touch 1G
}
if ([machine isEqualToString:@"iPod2,1"]) {
  // iPod touch 2G
}
if ([machine isEqualToString:@"iPod3,1"]) {
  // iPod touch Late2009
}

 或者

- (NSString *) platform
{
  size_t size;
  sysctlbyname("hw.machine", NULL, &size, NULL, 0);
  char *machine = malloc(size);
  sysctlbyname("hw.machine", machine, &size, NULL, 0);///-----get device struct info

  /*
  Possible values:
  "iPhone1,1" = iPhone 1G
  "iPhone1,2" = iPhone 3G
  "iPhone2,1" = iPhone 3GS
  "iPod1,1"   = iPod touch 1G
  "iPod2,1"   = iPod touch 2G
  */
  NSString *platform = [NSString stringWithCString:machine];

  free(machine);
  return platform;
}