Is there a "flatMap" method in the library?

[vkhorikov]

Is there a "flatMap" method in the library?

[vkhorikov]

In the library, Map is basically just for transforming a Result<T> into a Result<K>, this is not a fully-fledged Map from functional languages. Right now, there are only versions of this operation in OnSuccess and OnFailure methods. I guess what you are looking for is an overload for the OnBoth method so that the 3rd line in your sample would execute despite the previous outcome?

[solvingj]

Indeed this would not be a canonical Flatmap either, but in this case we would want a FlatMap to expect a Result<Result<T>> and just give us the object of type T in the lambda if the inner Result was a success. I think the harder part would be that we would want an inner Fail to be handled the same as if it were a top level fail as well.

If that doesn't make sense I can write up a proper example.

Edit: apparently markdown hid the T in Result<Result<T>>

[solvingj]

While this worked easily several times, in other cases it's throwing an exception that "There is no value for failure".

[solvingj]

Since result.Value only works if there are no errors, I'm now using this instead:

            .OnSuccess(result => result.Value)
            .OnFailure(error => Result.Fail(error));

Obviously this is sub-optimal for a few reasons. Not only is it unsightly, I also think I'm losing the type in the Fail condition. This might not be an issue though, I'm not sure.

Eventually I'll probably try to create FlatMap and submit a PR, if you could just let me know if you'd be willing to entertain such a PR.

[solvingj]

It turns out that the solution was just to use OnSuccess instead of Map.

Map should only be used if the function following it returns a value which does is not of type "Result"