let res = String(str.characters.filter { $0 != " " }) //去除空格

//过滤特殊符号

NSString *str2 = [passwdInput.text stringByTrimmingCharactersInSet:[NSCharacterSetwhitespaceAndNewlineCharacterSet]];NSCharacterSet *set = [NSCharacterSet characterSetWithCharactersInString:@"@／：；（）¥「」＂、[]{}#%-*+=_\\|~＜＞$€^•'@#$%^&*()_+'\""];