ios定义集合

1、定义常量
extern NSString *const UMShareToSina;

2、定义block
typedef void (^UMSocialSnsPlatformClickHandler)(UIViewController *presentingController, UMSocialControllerService * socialControllerService, BOOL isPresentInController);

宏定义
1、 弱引用
#define XSWeakSelf __weak typeof(self) weakSelf = self;

1、定义枚举
typedef  enum WKDataDetectorTypes : NSUInteger{
...
} WKDataDetectorTypes;