正则：数字、字母、符号至少两种

-(BOOL)judgePassWordLegal:(NSString*)pass{

    if(pass.length>8) {

        // 数字、字母、符号至少两种

        NSString * regex = @"^(?=.*[a-zA-Z0-9].*)(?=.*[a-zA-Z\\W].*)(?=.*[0-9\\W].*).{6,20}$";

        NSPredicate * pred = [NSPredicate predicateWithFormat:@"SELF MATCHES %@", regex];

        return[prede valuateWithObject:pass];

    }

    return false;

}