iOS开发常用的宏
#define screen_width ([uiscreen mainscreen].bounds.size.width)
#define screen_height ([uiscreen mainscreen].bounds.size.height)
#define safe_release(x) [x release];x=nil
#define ios_version [[[uidevice currentdevice] systemversion] floatvalue]
#define currentsystemversion ([[uidevice currentdevice] systemversion])
#define currentlanguage ([[nslocale preferredlanguages] objectatindex:0])
#define background_color [uicolor colorwithred:242.0/255.0 green:236.0/255.0 blue:231.0/255.0 alpha:1.0]
//use dlog to print while in debug model
#ifdef debug
# define dlog(fmt, ...) nslog((@"%s [line %d] " fmt), __pretty_function__, __line__, ##__va_args__);
#else
# define dlog(...)
#endif
#define isretina ([uiscreen instancesrespondtoselector:@selector(currentmode)] ? cgsizeequaltosize(cgsizemake(640, 960), [[uiscreen mainscreen] currentmode].size) : no)
#define iphone5 ([uiscreen instancesrespondtoselector:@selector(currentmode)] ? cgsizeequaltosize(cgsizemake(640, 1136), [[uiscreen mainscreen] currentmode].size) : no)
#define ispad (ui_user_interface_idiom() == uiuserinterfaceidiompad)
#if target_os_iphone
//iphone device
#endif
#if target_iphone_simulator
//iphone simulator
#endif
//arc
#if __has_feature(objc_arc)
//compiling with arc
#else
// compiling without arc
#endif
//g－c－d
#define back(block) dispatch_async(dispatch_get_global_queue(dispatch_queue_priority_default, 0), block)
#define main(block) dispatch_async(dispatch_get_main_queue(),block)
#define user_default [nsuserdefaults standarduserdefaults]
#pragma mark - degrees/radian functions
#define degreestoradian(x) (m_pi * (x) / 180.0)
#define radiantodegrees(radian) (radian*180.0)/(m_pi)
#pragma mark - color functions
#define rgbcolor(r,g,b) [uicolor colorwithred:(r)/255.0f green:(g)/255.0f blue:(b)/255.0f alpha:1]
#define rgbacolor(r,g,b,a) [uicolor colorwithred:(r)/255.0f green:(g)/255.0f blue:(b)/255.0f alpha:(a)]
#define width [[uiscreen mainscreen] bounds].size.width
#define height [[uiscreen mainscreen] bounds].size.height