Question

I am using the repository pattern and was wondering about what data type I should return. In my database I have a string that is variable length that needs to be broken up based off of fixed lengths. I was initially thinking of passing out the string and letting the service layer do the parsing based on the lengths of the configured columns. I dont really like the idea of passing a string out of the repository layer, would rather pass out a complete object. Passing out the string seems like not enough separation of responsibility, but having the repository having to go to another method to get how the string should be parsed and doing the parsing seems like too much work for the repo. Any suggestions of what should be the responsibility of the repo and service in this case?

Answer 1

Since the Repository is supposed to act as a collection of in memory objects, it should return an instance of whatever type of object your application is expecting to deal with. If your application expects a parsed object, you should return that.

Relying on some service to do the parsing is all a part of your infrastructure anyway. In most Repository implementations you have to do something with your persisted data before you return it, so this is a good thing.

For example, if your Repository is returning a Domain layer object, but your persistence is using L2S, you might want to map the L2S data to the domain object. You would need to rely on something outside the repository to do this. Call it a service or whatever, you probably don’t want to kluge the repository code with the mapping.