Foundation Renaming Question


(Joe Bell) #1

Howdy.

I've been building (on Linux) the latest off of master for Swift and the
accompanying swift-corelibs-foundation. I can see where the great renaming
is in full swing and have been updating my code accordingly.

One area where I'm a bit confused is with the new API for
NotificationCenter and Notification.

In the past bare strings were acceptable for postNotificationName and
addObserverForName. Yet now constructing a Notification and
Notification.Name seem to be a bit unwieldy. Example:

let ConnectedNotification =
Notification(name:Notification.Name(rawValue:"ConnectedNotification"))

That seems to be quite convoluted and I'm not sure why there isn't a
convenience init that allows for

let ConnectedNotification = Notification(name:"ConnectedNotification")

Then, the APIs for post and observe seem to be mismatched:

NotificationCenter.defaultCenter().postNotification(ConnectedNotification)

vs.

NotificationCenter.defaultCenter().addObserverForName(ConnectedNotification.name)

I would think an addObserverForNotification would be more appropriate here.

Finally, combining topics a bit, but they are related:

let ConnectedNotification =
Notification(name:Notification.Name(rawValue:"ConnectedNotification"))
let DisconnectedNotification =
Notification(name:Notification.Name(rawValue:"DisconnectedNotification"))

These notifications are for the same API, so I'm assuming I'm "doing this
wrong" and that the more Swifty way would be too put these in a struct or
enum, so I'm curious as to what folks recommend.

Thanks!

···

--
Joseph Bell
http://dev.iachieved.it/iachievedit/
@iachievedit


(Brent Royal-Gordon) #2

In the past bare strings were acceptable for postNotificationName and addObserverForName. Yet now constructing a Notification and Notification.Name seem to be a bit unwieldy. Example:

let ConnectedNotification = Notification(name:Notification.Name(rawValue:"ConnectedNotification"))

That seems to be quite convoluted and I'm not sure why there isn't a convenience init that allows for

let ConnectedNotification = Notification(name:"ConnectedNotification")

You're running into trouble because you're not following the typical pattern for these types. The intended usage is:

* You assign the Notification.Name to a constant.

  class ChatConnection {
    static let didConnect = Notification.Name("ChatConnection.didConnect")
    …
  }

* You create Notification instances on demand, or preferably let the NotificationCenter make them for you.

  extension ChatConnection {
    func connectionCompleted() {
      NotificationCenter.default().post(name: ChatConnection.didConnect, object: self)
    }
  }

Individual Notifications are meant to be one-off instances. If you follow this pattern, you'll find that the API design suddenly makes a lot more sense!

···

--
Brent Royal-Gordon
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