OC常用小方法

字符串判空：

if ((value == nil) || value == (NSString *)[NSNull null] || (value.length == 0)){ ... }

字典安全取值：

#define    SafeObjectForKey(dic,key)    [dic objectForKey:key] == nil || [[dic objectForKey:key] isKindOfClass:[NSNull class]] ? @"" : [dic objectForKey:key]