Suggestion: Filter on FetchRequestController should not perform fetch

[AnthonyMDev]

I'd like to suggest that the filter(predicateClosure:) function on FetchRequestController should not automatically perform the fetch again.

I have two reasons for this:

1. Initializing the FetchRequestController with a fetch request does not perform the fetch. The user would assume that adding a filter would have the same effect. The user already knows they must call performFetch() in one case. We should keep this consistent.
2. I have a use case in which I would like to add multiple new filters to my FetchRequestController simultaneously. Currently, it is performing the fetch multiple times unnecessarily. To get around that, I'm having to create my NSPredicate manually and then use the refreshWithPredicate(_: keepOriginalPredicate:) method.

Thoughts?

[vmartinelli]

About all the filter related issues, I think it will be better to always have an option to performFetch or not, or remove the “auto fetching” and let the user decide where she/he wants to perform the fetch. Also it would be nice to think about the FetchRequestController will fit the new Core Data features (WWDC 16) from now.

[AnthonyMDev]

So you are open to a PR to make this change then? I'll go ahead and make a PR in the morning.

I haven't watched the Core Data sessions from WWDC yet, but I will very soon. We should probably open another ticket to discuss any suggested changes to fit the new features.

[vmartinelli]

Yes. :-)

About the WWDC, I think the Core Data session will on Friday.