OC 密码验证（正则+连续输入+输入过于简单判断）

 + (BOOL) password:(NSString *)password

 {
 NSString *pattern = @"[a-zA-Z0-9]{6,19}+$";
 NSPredicate *pred = [NSPredicate predicateWithFormat:@"SELF MATCHES %@", pattern];
 BOOL isMatch = [pred evaluateWithObject:password];
 if (isMatch) {
 int count = 0;
 NSString *newPassword = [password substringToIndex:1];
 for (int i = 0; i < password.length; i++) {
 NSString *newPassword1;
 if (i == 0) {
 newPassword1 = [password substringToIndex:i + 1]; //当 i 为 0 的时候  取下表为 1 的字符串
 }else{
 //当 i 大于 0 时 我们取下标为 i + 1 新的string.length 为 i 个 所有我们再从后面往前面取
 newPassword1 = [[password substringToIndex:i + 1] substringFromIndex:i];
 }
 if ([newPassword1 isEqualToString:newPassword]) {
 count++;
 }
 }
 if (count == password.length) {
 return NO; // 这里说明 count个相同的字符串，也就是所有密码输入一样了
 }
 if ([password isEqualToString:@"123456"] ||
 [password isEqualToString:@"qwerty"] ||
 [password isEqualToString:@"654321"]) return NO;
 }
 return isMatch;
 }