Add ensure hook

[ayrat555]

Sometimes there are situations when an interactor operates with sensible resources, for example, with files. In my opinion, we should have a mechanism to do a final processing on that resources in case an error occurs.

Currently I'm creating a lot of files in my system, location of that files are calculated during execution of interactor and they are available only through interactor's context. So deleting them with ensure_hook solves my problem.

I hope this feature will be useful.

P.S. I will add more tests and docs if everything is ok.

[ayrat555]

@laserlemon what is your opinion?

[danlo]

+1

[gaffneyc]

I'm looking at this and #206 and I don't fully understand the use case or how an Interactor level ensure wouldn't be covered by the ensure mechanism in Ruby itself.

In your example it sounds like you have one Interactor which opens the file and puts it in the Context, several other Interactors that act on the file, then it is closed at some point. The ensure hook would make the pattern more complete by putting the close near the open. Without more context it seems like it could be solved by reorganizing the Interactors such that the processing chain is passed an open file from code that is also responsible for closing the file.

I'm open to a more concrete example for how ensure would help solve a problem. It seems like there is a want for it or a need to better document how to scope Interactors to avoid that need.