Programming pattern / architectural question
architecture, design-patterns, domain-driven-design
Solution
I would use some form of Inversion Of Control.
To be specific, I would have an interface called IIBANValidator. The various means of validating the IBAN should implement that interface. For example:
interface IBANValidator {
Boolean Validate(string iban);
}
class SqlBanValidator : IBANValidator {
public bool Validate(string iban) {
// make the sql call to validate..
throw new NotImplementedException();
}
}
Then, I would have a method in my BankAccount class which accepted an object that implements IIBANValidator and the IBAN number and was structured like (not optimized by any stretch):
Boolean SetIBAN(IIBANValidator validator, String iban) {
Boolean result = false;
if (validator.Validate(iban)) {
Iban = iban;
result = true;
}
return result;
}
At this point your BankAccount class would not have to have a dependency on your validators, you could swap them out at will, and ultimately it's very clean.
The final code would look something like:
BankAccount account = new BankAccount();
account.SetIBAN(new SqlBanValidator(), "my iban code");
Obviously at runtime you could pass any validator instance you wanted.
Problem
I am currently working on a project where I have a BankAccount entity for some other entity. Each bank account as a reference to a bank entity, an account number and optionally an IBAN. Now since an IBAN can be validated, how can I ensure that when the IBAN is set for an account is valid. What would be a clean architectural approach? I currently have a domain layer without any reference to any other layer and I like this clean approach (I was inspired by Eric Evans DDD). Fortunately the IBAN validation can be performed without accessing any outside system so in this case I could have something like ``` puclic class BankAccount { public string Iban { set { // validation logic here } } } ``` But now I was thinking what approach I would use if the IBAN validation requires an SQL server check for example, or an external dll. How would I implement that. Would I create an IBAN value object which is passed to a service, that decides whether the IBAN is valid or not and after that set it to the BankAccount entity? Or would I create a factory which is allowed to instanstiate IBANs and performs validation before? Thanks for your help!