Coordinator Cleanup

[heyltsjay]

A few things here:

• Simplifies Coordinator down to class Coordinator: NSObject {}
• Moves presentation style to be determined by parents
• Adopts a pattern to attach to children so that Coordinator lifecycles are ultimately determined by the View/Navigation hierarchy. This reduces the need to hold any reference to children and eliminates the need to hold strong references to children, which is now forbidden.
• Removes some noise from the demo code to just demonstrate the pattern and little else.

[jvisenti]

I generally like the ownership change, but am a bit fearful that since attach is required everywhere someone will forget it somewhere and cause a hard-to-track-down bug. Any way it can be more enforced?

[jvisenti]

#nth Add a should **NOT** hold strong references to coordinators somewhere in here. Just to contrast with how we used to always hold strong refs to make sure they didn't go away

[jvisenti]

#pp Instead of guarding with early returns, use if/else. This bit me on a project where I wanted to do something after the correct coordinator was chosen, and had to do it with a defer.

[jvisenti]

#pp I don't see why this would be in an extension instead of the class declaration body. Only thing I can think of is that you didn't want the methods to be overridable (since you can't override non @objc functions defined in an extension), in which case you could just mark them final. I personally would rather they be overridable incase a subclass wanted to do something additional when attached. Maybe.

[heyltsjay]

It's mostly in an extension to try to box up the code that deals with associated objects

[jvisenti]

In the same file though. And has the side effect of limiting inheritance.

[heyltsjay]

I had originally toyed with a CoordinatorProtocol: class, NSObjectProtocol and Coordinator: NSObject, CoordinatorProtocol and was considering trying to expose in an extension on the protocol, but I waffled on if a protocol was valuable at all

[heyltsjay]

The Attach/Detach behavior could technically just be an extension on AnyObject but that seems ripe for abuse

[chrisballinger]

Is this something that should be revisited soon?

[heyltsjay]

Hey @chrisballinger, Rob V and I are currently taking the pattern for a spin. We're curious if the attach pattern in combination with style rules (only holding weak references to children) will help iron out some common ownership issues that come from typical Coordinator/Controller patterns.

[heyltsjay]

Seems a little too opinionated to merge into the template before someone gets some insight by using it in a client project. Open to feedback!