根据屏幕尺寸和分辨率，ios现在数起来有6个版本。iOS 设备现有的分辨率如下：
iPhone/iPod Touch
普通屏                         　 320像素 x 480像素       iPhone 1、3G、3GS，iPod Touch 1、2、3
3：2 Retina 屏           　　640像素 x 960像素        iPhone 4、4S，iPod Touch 4
16：9 Retina 屏               640像素 x 1136像素      iPhone 5，iPod Touch 5iPad
普通屏         　　　　　　   768像素 x 1024像素      iPad 1， iPad2，iPad mini
Retina屏     　　　　         1536像素 x 2048像素     New iPad，iPad 4UIDevice+Resolutions.h//
//  UIDevice+Resolutions.h
//  Test_common
//
//  Created by wangzhipeng on 13-1-30.
//  Copyright (c) 2013年 com.comsoft. All rights reserved.
//

#import enum {// iPhone 1,3,3GS 标准分辨率(320x480px)UIDevice_iPhoneStandardRes      = 1,// iPhone 4,4S 高清分辨率(640x960px)UIDevice_iPhoneHiRes            = 2,// iPhone 5 高清分辨率(640x1136px)UIDevice_iPhoneTallerHiRes      = 3,    // iPad 1,2 标准分辨率(1024x768px)UIDevice_iPadStandardRes        = 4,    // iPad 3 High Resolution(2048x1536px)UIDevice_iPadHiRes              = 5
}; typedef NSUInteger UIDeviceResolution;@interface UIDevice (Resolutions){}+ (UIDeviceResolution) currentResolution;+ (BOOL)isRunningOniPhone5;+ (BOOL)isRunningOniPhone;@endUIDevice+Resolutions.m//
//  UIDevice+Resolutions.m
//  Test_common
//
//  Created by wangzhipeng on 13-1-30.
//  Copyright (c) 2013年 com.comsoft. All rights reserved.
//

#import "UIDevice+Resolutions.h"@implementation UIDevice (Resolutions)+ (UIDeviceResolution) currentResolution {if(UI_USER_INTERFACE_IDIOM() == UIUserInterfaceIdiomPhone){if ([[UIScreen mainScreen] respondsToSelector: @selector(scale)]) {CGSize result = [[UIScreen mainScreen] bounds].size;result = CGSizeMake(result.width * [UIScreen mainScreen].scale, result.height * [UIScreen mainScreen].scale);if (result.height <= 480.0f)return UIDevice_iPhoneStandardRes;return (result.height > 960 ? UIDevice_iPhoneTallerHiRes : UIDevice_iPhoneHiRes);} elsereturn UIDevice_iPhoneStandardRes;} elsereturn (([[UIScreen mainScreen] respondsToSelector: @selector(scale)]) ? UIDevice_iPadHiRes : UIDevice_iPadStandardRes);
}+ (BOOL)isRunningOniPhone5{if ([self currentResolution] == UIDevice_iPhoneTallerHiRes) {return YES;}return NO;
}+ (BOOL)isRunningOniPhone{return (UI_USER_INTERFACE_IDIOM() == UIUserInterfaceIdiomPhone);
}@end