判断某个字符串是否为空
if(string== nil ||string==NULL)
if( [string isKindOfClass:[NSNull class]] )
if( [[string stringByTrimmingCharactersInSet:[NSCharacterSet whitespaceChara
判断某个字符串是否为空
if(string== nil ||string==NULL)
if( [string isKindOfClass:[NSNull class]] )
if( [[string stringByTrimmingCharactersInSet:[NSCharacterSet whitespaceChara