如何简化验证检查代码？

Question

I have code for validation:

public IDictionary<string, string> ValidateForDeletion(Account ac)
        {
            var account = _accountRepository.GetPkRk(ac.PartitionKey, ac.RowKey);
            if (account == null)
            {
                _errors.Add("", "Account does not exist");
                return _errors;
            }
            if (_productRepository.GetPk("0000" + ac.RowKey).Count() != 0)
            {
                _errors.Add("", "Account contains products");
                return _errors;
            }
            return _errors;
        }

All I see there are many many "return _errors" lines. Is there any way that I could tidy up the code and keep the functionality? I saw one example using yield but not sure if I could use that for this method.

Answer 1

public IDictionary<string, string> ValidateForDeletion(Account ac)
{
    var account = _accountRepository.GetPkRk(ac.PartitionKey, ac.RowKey);
    if (account == null)
    {
        _errors.Add("", "Account does not exist");
    }
    else if (_productRepository.GetPk("0000" + ac.RowKey).Count() != 0)
    {
        _errors.Add("", "Account contains products");
    }
    return _errors;
}

This will get rid of your multiple return statements

Answer 2

Well you can always pull the extra cruft into its own method:

public IDictionary<string, string> ValidateForDeletion(Account ac)
{
  var account = _accountRepository.GetPkRk(ac.PartitionKey, ac.RowKey);
  return BuildErrorsList(account);
}

private IDictionary<string, string> BuildErrorsList(Account account)
{
  if (account == null)
     _errors.Add("", "Account does not exist");
  if (_productRepository.GetPk("0000" + ac.RowKey).Count() != 0)
      _errors.Add("", "Account contains products");
  return _errors;
}

As good guideline is that each method should work on one level of abstraction, otherwise you probably want pull the "lower level" stuff into its own method.

Answer 3

public IEnumerable<ValidationResult> ValidateForDeletion(Account ac)
{
    var account = _accountRepository.GetPkRk(ac.PartitionKey, ac.RowKey);
    if (account == null)
    {
        yield return new ValidationResult("Account does not exist");
    }
    if (_productRepository.GetPk("0000" + ac.RowKey).Count() != 0)
    {
        yield return new ValidationResult("Account contains products");
    }
}

Answer 4

1. It's not ideal that your method is changing state (the _errors field) whilst also returning the field — this makes it a bit confused. Normally you would either have a method that changes the state (change _errors ) or have a function that returns a result.

2. The ValidateForDeletion method returns after the first failure rather than add all errors to the dictionary. Are you sure that is correct behaviour?

If were refactoring this, I would probably get rid of ValidateForDeletion 's side-effects (changes to fields) and have it return IEnumerable<string> . I would also make it perform the complete set of validations. Obviously this will have ramifications on the calling code so you will have to make sure you do not break anything.

public IEnumerable<string> ValidateForDeletion(Account ac)
{
    var account = _accountRepository.GetPkRk(ac.PartitionKey, ac.RowKey);
    if (account == null)
    {
        yield return "Account does not exist";
    }

    if (_productRepository.GetPk("0000" + ac.RowKey).Count() != 0)
    {
        yield return "Account contains products";
    }

    return;
}

Answer 5

You could do something similar to yield. If you think about passing by reference, you can have validation code within your objects or repositories.

For example, I am validating to see if an account can be deleted, I can use an IValidateDelete interface on Account that has this method:

bool account.IsValidForDeletion(ref ValidationErrors validationErrors);

Then I can call it and pass in my empty validation errors method. If the result is true, you're good to go. If it's false, it will have appended the validation error to the internal list in the ValidationErrors object.

public bool IsValidForDeletion(ref Validationerrors validationErrors)
{
//
if (something is valid)
{
  return true;
}

validationErrors.AddError("Something is wrong, this cannot be deleted");

return false;
}

Now you can run through all your methods like this:

public ValidationErrors ValidateABunchOfStuff()
{
   ValidationErrors errors = new ValidationErrors();

   account.IsValidForDeletion(errors);
   product.IsValidForDeletion(errors);
   cake.IsValidForDeletion(errors);

   return errors;
}