#define isRetina ([UIScreen instancesRespondToSelector:@selector(currentMode)] ? CGSizeEqualToSize(CGSizeMake(640,960), [[UIScreen mainScreen] currentMode].size) : NO)

 

 

NSString*deviceType =[UIDevice currentDevice].model; if([deviceType isEqualToString:@"iPhone"]){
        //iPhone } elseif([deviceType isEqualToString:@"iPod touch"]){
        //iPod Touch } else{
        //iPad }

使用#if：

#ifdef  UI_USER_INTERFACE_IDIOM  

//注意此处没有括号

//UI_USER_INTERFACE_IDIOM 是枚举类型结构体，内有

typedefenum {
   #if __IPHONE_3_2 <= __IPHONE_OS_VERSION_MAX_ALLOWED     UIUserInterfaceIdiomPhone,           // iPhone and iPod touch style UI   0     UIUserInterfaceIdiomPad,             // iPad style UI                    1 #endif } UIUserInterfaceIdiom;

 

//而UI_USER_INTERFACE_IDIOM()是定义的宏

#define UI_USER_INTERFACE_IDIOM() ([[UIDevice currentDevice] respondsToSelector:@selector(userInterfaceIdiom)]?[[UIDevice currentDevice] userInterfaceIdiom]:UIUserInterfaceIdiomPhone)

  #define IS_IPAD() (UI_USER_INTERFACE_IDIOM()==UIUserInterfaceIdiomPad) #else   #define IS_IPAD() (false) #endif

#if UI_USER_INTERFACE_IDIOM()==0  //==UIUserInterfaceIdiomPhone @implementationUINavigationBar(Custom height) -(CGSize)sizeThatFits:(CGSize)size {
        CGSize newSize =CGSizeMake(self.frame.size.width,44+BreadCrumbBarHeight-1);     return newSize; }     @end #endif

 

 

 

判断当前ios版本是否等于5.0

#ifdef __IPHONE_5_0 　　//if (__IPHONE_OS_VERSION_MAX_ALLOWED >= __IPHONE_5_0){      float version = [[[UIDevice currentDevice] systemVersion] floatValue];        if (version >= 5.0) 　　{        [[NSNotificationCenter defaultCenter] addObserver:self selector:@selector(keyBoardWillChange:) name:UIKeyboardWillChangeFrameNotification object:nil];    }#else    [[NSNotificationCenter defaultCenter]addObserver:self selector:@selector(keyBoardWillChange:) name:UIKeyboardWillShowNotification object:nil];        [[NSNotificationCenter defaultCenter]addObserver:self selector:@selector(keyBoardWillChange:) name:UIKeyboardWillHideNotification object:nil];#endif