C#•3y ago

How to handle results from a service [Answered]

I have the following service:

public interface ITodoService {
  Task<IEnumerable<TodoList>> GetListsAsync();
  Task<TodoList?> GetListFromIdAsync(Guid id);
  Task<TodoItem?> GetItemFromIdAsync(Guid id);
  Task<TodoItem?> AddItemToList(Guid listId, AddItemDto item);
}

public interface ITodoService {
  Task<IEnumerable<TodoList>> GetListsAsync();
  Task<TodoList?> GetListFromIdAsync(Guid id);
  Task<TodoItem?> GetItemFromIdAsync(Guid id);
  Task<TodoItem?> AddItemToList(Guid listId, AddItemDto item);
}

The nullable returns in some of the methods in this case indicate that the method may not find anything, except this feels a bit clunky as just a nullable return doesn't really communicate much intention and I end up having to in my API endpoints have specific cases for whether the item returned was nullable. In addition, more errors than just the item not being found could occur. I really don't wanna have to use a specific DU structure for every single method and hardcode what errors could occur as, well, I'd have to update it every time a new possible error could happen. I think I should use something like Remora.Results or some other functional result library, though I'd still like some feedback.

10 Replies

TheBoxyBear•3y ago

In asp mvc there's IActionResult that encapsulates the result or any errors if present Complete with implicit conversions so you don't have to create a result when returning

jcotton42•3y ago

That's not general purpose though Afaik

ThinkerOP•3y ago

Yeah, I'm using currently Microsoft.AspNetCore.Http.IResult as the return from my endpoints, although I don't really wanna use this in my services as first and foremost the project doesn't even have a reference to any ASP.NET library, and secondly I feel like services shouldn't be bothered with endpoint-level concerns such as what status code to return.

TheBoxyBear•3y ago

Task itself also stores its error state

ThinkerOP•3y ago

Not the kind of error state you can easily use as a "result" type state

jcotton42•3y ago

I'd use Remora

ThinkerOP•3y ago

Now the only issue is the fact that Remora's type is also called IResult catsip

pox•3y ago

We use a Either class that either holds the item or and enum error code. Not a fan of result types that don't have hard typed errors Saw now that you don't want hardcoded errors

ThinkerOP•3y ago

Eh, I'll figure something out

Accord•3y ago

✅ This post has been marked as answered!

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How to handle results from a service [Answered]

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