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)

//单例类
#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)