Convenience updates

[darrarski]

Added convenience methods for creating new or updating existing Entity objects.

extension CoreDataModelable where Self: NSManagedObject {
    static public func createInContext(context: NSManagedObjectContext, @noescape configure: Self -> ()) -> Self
    static public func updateInContext(context: NSManagedObjectContext, predicate: NSPredicate?, @noescape configure: Self -> ()) throws -> [Self]
    static public func updateOrCreateInContext(context: NSManagedObjectContext, predicate: NSPredicate?, @noescape configure: Self -> ()) throws -> [Self]
}

[rcedwards]

Thank you for your contribution to the BNR Core Data Stack. As a team we see these changes as a solid addition to any individual project, however in a framework setting, it would broaden our public API in a way that may not benefit the majority of CoreDataStack users.

From a technical preservative these changes are spot on (terrific comments, accompanying tests, sound code) and this is simply a strategic decision.

If you happen to create a separate repository for this CoreDataModelable extension, we'd be more than happy to link to it from our Wiki as a CoreDataStack add-on.

Thanks again!

[jeremy-w]

I've created an Add-Ons wiki page to collect add-ons.

[darrarski]

Sure, I understand your point. Could you provide some hints about creating add-ons? Should it be managed by some dependency manager like CocoaPods?

[jeremy-w]

I was thinking Carthage, but we could add a column for Pod name to that table to accommodate Podfiles, too.

I imagine people using their dependency manger of choice to pull in CoreDataStack + whatever sugar or extensions they'd like to have on top of it.

[rcedwards]

https://github.com/spark/spark-sdk-ios might be a good reference for a repo that has a dependency that is listed in both a podspec and Cartfile.

Here is a smaller example with just a podspec for an add on to AFNetworking https://github.com/steipete/AFDownloadRequestOperation