Auto Update

A simple Protocol Oriented Framework for writing easily-updatable, data-driven views.

Protocols

I’m using a Protocol called Unit because a game I’m making involves war stuff.

Model Protocol

protocol Unit {
    var name: String { get set }
    var id: String { get }
    var status: UnitStatus { get set }
}

I also need to be able to equate them.

func ==(lhs: Unit?, rhs: Unit?) -> Bool {
    return (lhs?.id == rhs?.id)
}

Now I’ll create a simple struct to conform to my Unit protocol.

struct Hero: Unit {
    var id: String
    var name: String
    var status: UnitStatus
}

View Protocol

Next is my view protocol for displaying a Unit. This will be shockingly called UnitView.

protocol UnitView {
    var unit: Unit? { get }
    func prepare(withUnit unit: Unit?)
}

I can add whatever I’d like into this protocol, but the magic happens in the prepare(withUnit unit: Unit?). I put all of my view updating code in prepare(withUnit unit: Unit?) and I’m good to go.

I need to extend the UnitView protocol for UIViews (you can also do UIViewControllers as well) so I can call autoUpdate(), which makes the view an observer of data store updates.

extension UnitView where Self: UIView {
    func autoUpdate() {
        NotificationCenter.default.addObserver(forName: NSNotification.Name.objectUpdated, object: nil, queue: OperationQueue.main) {
            [weak self] (notification: Notification) in

            guard let unit = notification.userInfo?["unit"] as? Unit else {
                return
            }

            if self?.unit == unit {
                self?.unit = unit
                self?.prepare(withUnit: unit)
            }
        }
    }
}

Once the autoUpdate() function is called in my view initialization, my views (or View Controllers) will update themselves.

Here is an example of a UICollectionViewCell conforming to UnitView ready to be auto updated.

class UnitCollectionViewCell: UICollectionViewCell, UnitView {

    var unit: Unit?

    @IBOutlet weak var nameLabel: UILabel!
    @IBOutlet weak var statusLabel: UILabel!

    override func awakeFromNib() {
        super.awakeFromNib()
        autoUpdate()
    }

    func prepare(withUnit unit: Unit?) {
        self.nameLabel.text = unit?.name
        self.statusLabel.text = unit?.face()
    }

    override func prepareForReuse() {
        super.prepareForReuse()
        prepare(withUnit: unit)
    }
}

Data Store

Another key component to the Auto Update framework is a data store to send out notifications to our UnitViews.

Here is all I need for a simple data store.

class DataStore {

    static let shared = DataStore()

    func update(object: Unit?) {
        guard let updatedUnit = object else {
            return
        }

        // save the object in whatever way you need to

        // notifies our UnitViews that a Unit was updated
        NotificationCenter.default.post(name: NSNotification.Name.objectUpdated, object: nil, userInfo: [Constants.objectKey: updatedUnit])
    }
}

🤙