下面提到的代码片段应该有帮助:

 if ([[UIDevice currentDevice] userInterfaceIdiom] == UIUserInterfaceIdiomPhone) {
   // iPhone device
 }
 else if ([[UIDevice currentDevice] userInterfaceIdiom] == UIUserInterfaceIdiomPad) {
   // iPad device
 }
 else {
  // Other device i.e. iPod
 }

我想添加一个私有API来检索设备的正面和外壳颜色:

UIDevice *device = [UIDevice currentDevice];
SEL selector = NSSelectorFromString([device.systemVersion hasPrefix:@"7"] ? @"_deviceInfoForKey:" :  @"deviceInfoForKey:");
if ([device respondsToSelector:selector]) {
    NSLog(@"DeviceColor: %@ DeviceEnclosureColor: %@", [device performSelector:selector withObject:@"DeviceColor"], [device performSelector:selector withObject:@"DeviceEnclosureColor"]);
}

我在博客上写过这方面的文章，并提供了一个示例应用程序:

http://www.futuretap.com/blog/device-colors/

你可以像这样使用UIDevice类:

NSString *deviceType = [UIDevice currentDevice].model;

if([deviceType isEqualToString:@"iPhone"])
    // it's an iPhone

以下是新模型的小更新:

- (NSString *) platformString{
    NSString *platform = [self platform];
    if ([platform isEqualToString:@"iPhone1,1"]) return @"iPhone 1G";
    if ([platform isEqualToString:@"iPhone1,2"]) return @"iPhone 3G";
    if ([platform isEqualToString:@"iPhone2,1"]) return @"iPhone 3GS";
    if ([platform isEqualToString:@"iPhone3,1"]) return @"iPhone 4";
    if ([platform isEqualToString:@"iPod1,1"])   return @"iPod Touch 1G";
    if ([platform isEqualToString:@"iPod2,1"])   return @"iPod Touch 2G";
    if ([platform isEqualToString:@"iPod3,1"])   return @"iPod Touch 3G";
    if ([platform isEqualToString:@"i386"])   return @"iPhone Simulator";
    return platform;
}

我在我的应用程序中使用这个。截至2012年12月。

- (NSString *) platformString {
    // Gets a string with the device model
    size_t size;  
    sysctlbyname("hw.machine", NULL, &size, NULL, 0);  
    char *machine = malloc(size);  
    sysctlbyname("hw.machine", machine, &size, NULL, 0);  
    NSString *platform = [NSString stringWithCString:machine encoding:NSUTF8StringEncoding];  
    free(machine); 

    if ([platform isEqualToString:@"iPhone1,1"])    return @"iPhone 2G";
    if ([platform isEqualToString:@"iPhone1,2"])    return @"iPhone 3G";
    if ([platform isEqualToString:@"iPhone2,1"])    return @"iPhone 3GS";
    if ([platform isEqualToString:@"iPhone3,1"])    return @"iPhone 4";
    if ([platform isEqualToString:@"iPhone3,2"])    return @"iPhone 4";
    if ([platform isEqualToString:@"iPhone3,3"])    return @"iPhone 4 (CDMA)";    
    if ([platform isEqualToString:@"iPhone4,1"])    return @"iPhone 4S";
    if ([platform isEqualToString:@"iPhone5,1"])    return @"iPhone 5";
    if ([platform isEqualToString:@"iPhone5,2"])    return @"iPhone 5 (GSM+CDMA)";

    if ([platform isEqualToString:@"iPod1,1"])      return @"iPod Touch (1 Gen)";
    if ([platform isEqualToString:@"iPod2,1"])      return @"iPod Touch (2 Gen)";
    if ([platform isEqualToString:@"iPod3,1"])      return @"iPod Touch (3 Gen)";
    if ([platform isEqualToString:@"iPod4,1"])      return @"iPod Touch (4 Gen)";
    if ([platform isEqualToString:@"iPod5,1"])      return @"iPod Touch (5 Gen)";

    if ([platform isEqualToString:@"iPad1,1"])      return @"iPad";
    if ([platform isEqualToString:@"iPad1,2"])      return @"iPad 3G";
    if ([platform isEqualToString:@"iPad2,1"])      return @"iPad 2 (WiFi)";
    if ([platform isEqualToString:@"iPad2,2"])      return @"iPad 2";
    if ([platform isEqualToString:@"iPad2,3"])      return @"iPad 2 (CDMA)";
    if ([platform isEqualToString:@"iPad2,4"])      return @"iPad 2";
    if ([platform isEqualToString:@"iPad2,5"])      return @"iPad Mini (WiFi)";
    if ([platform isEqualToString:@"iPad2,6"])      return @"iPad Mini";
    if ([platform isEqualToString:@"iPad2,7"])      return @"iPad Mini (GSM+CDMA)";
    if ([platform isEqualToString:@"iPad3,1"])      return @"iPad 3 (WiFi)";
    if ([platform isEqualToString:@"iPad3,2"])      return @"iPad 3 (GSM+CDMA)";
    if ([platform isEqualToString:@"iPad3,3"])      return @"iPad 3";
    if ([platform isEqualToString:@"iPad3,4"])      return @"iPad 4 (WiFi)";
    if ([platform isEqualToString:@"iPad3,5"])      return @"iPad 4";
    if ([platform isEqualToString:@"iPad3,6"])      return @"iPad 4 (GSM+CDMA)";

    if ([platform isEqualToString:@"i386"])         return @"Simulator";
    if ([platform isEqualToString:@"x86_64"])       return @"Simulator";

    return platform;
}  

只是将iPhone 4S设备代码添加到这个线程…

iPhone 4S将返回字符串@"iPhone4,1"。