ObjectiveC: Nullability, Lightweight Generics

[Adlai-Holler]

Killer framework! This PR updates the public API Objective-C for Xcode 7 so the framework integrates with Swift better plus adds some compiler checks.

[levi]

Thanks for this, @adly-holler. I was just adding these this morning and you beat me to it :). Be sure to update the .travis.yaml to support the syntax additions: osx_image: xcode7.

[Adlai-Holler]

Ah! Thanks @levi , done and done!

[SRandazzo]

yyyaaaaassssssss!!!! 👍 so much on this! Thanks

[Adlai-Holler]

@appleguy If this is too big a change for one external PR, I'd be glad to target a separate branch so others can work on it too

[appleguy]

Hey @adly-holler — love your enthusiasm, as I was starting to use this syntax in some of my own work :). I was hesitant to change the build system configuration right before the NSSpain announcement of 2.0. It's still not showing a clean build, but let's retry it and see if we can get it in!

[Adlai-Holler]

@appleguy Sweet! I got it to the point where it'll build on Travis, but now some tests are failing because of missing implementations of category properties like [_ASDisplayLayer asyncdisplaykit_isAsyncTransactionContainer]: unrecognized selector. I added an implementation for one of them, and then it crashed on a different one.

I don't quite understand how these methods were ever getting implemented in the first place. All I can find is @dynamic [name] specifiers with no implementation code in sight. Any pointers? @nguyenhuy ?

[appleguy]

@adly-holler if you roll back your commits, does it start building? Maybe try submitting a PR with the Xcode 7 travis build image alone, without adopting any new language features, and see if that has the same issue?

I'm pretty sure ASDK builds with Xcode 7, but perhaps not on Travis.

[appleguy]

This change allowed me to build & run unit tests locally with Xcode 7 Beta 5. Downloading the final version, but it may not finish before I get on the plane tomorrow (going very slowly on hotel internet).

#670

[appleguy]

Sadly there is zero traction whatsoever on the Apple issues, so it is going to take months to land this. I am going to close the PR until we are on Xcode 7, and then reopen.

[appleguy]

I worked around Apple's frustrating, still-unfixed bug with @dynamic properties on CALayer by avoiding use of them. It's a suboptimal solution as we lose certain capabilities, but I'm excited to get this in. A truly happy Christmas 2015, lol!

#994

[appleguy]

Now superseded by #995 as this couldn't be merged with master. Getting close to 1000!