ios 宏

//字符串宏

#define EMPTY_STRING(string) \
    ( [string isKindOfClass:[NSNull class]] || \
    string == nil || [string isEqualToString:@""])

#define GET_STRING(string) (EMPTY_STRING(string) ? @"" : string)

//單例類
#define DECLARE_SINGLETON(cls_name, method_name)\
    + (cls_name*)method_name;

#define IMPLEMENT_SINGLETON(cls_name, method_name)\
    + (cls_name *)method_name {\
        static cls_name *method_name;\
        static dispatch_once_t onceToken;\
        dispatch_once(&onceToken, ^{\
            method_name = [[cls_name alloc] init];\
        });\
        return method_name;\
    }

//本地化
#define L(s) NSLocalizedString((s), nil)