Pair iOS devices by clinking them together, then track the application state of paired remote peers over BLE whenever they're in range.

To start pairing with new peers, first register for Clink notifications by calling:

let token = Clink.shared.addNotificationHandler { [weak self] (notif: Clink.Notification) in
    // ...
}

Then start scanning for eligible peers by calling:

Clink.shared.startClinking()

Once a remote peer that is actively "clinking" comes within range, your notification handler will be called and passed in a notification of case .clinked with the discovered peer ID as an associated type – like so:

let token = Clink.shared.addNotificationHandler { [weak self] (notif: Clink.Notification) in
    switch notif {
    case .clinked(let discoveredPeerId):
        //- dismiss discovery progress ui, show success conformation UI
    }
}

Once a remote peer has been "clinked", a connection to it will maintained / reestablished whenever that peer is within BLE range.

Clink peers can share arbitrary application state data with other connected peers by calling:

Clink.set(value: someValue, forProperty: somePropertyName)

When a peer updates their local state data by calling Clink.set(value: Any, forProperty: String) all registered notification handlers of all connected peers will be called, this time being passed in a clink notification of case .updated, with the updated peer ID as an associated type:

let token = Clink.shared.addNotificationHandler { [weak self] (notif: Clink.Notification) in
    switch notif {
    case .updated(let updatedPeerId):
        // update UI etc...
    }
    
    //...
}

Any peer initializations, connections, updates, disconnections, and errors caught by Clink call all registered notification blocks as well, passing a notification of case initial(connectedPeerIds: [PeerId]) , case connected(peerWithId: PeerId), case updated(peerWithId: PeerId), case disconnected(peerWithId: PeerId), or case error(OpperationError) respectively:

let token = Clink.shared.addNotificationHandler { [weak self] (notif: Clink.Notification) in

switch notif {
    case .initial(let connectedPeerIds: [Clink.Peer)
        //- called when notification handler is first registered
    case .connected(let peerId):
        //- handle peer connection
    case .updated(let peerId):
        //- handle remote peer data update
    case .disconnected(let peerId):
        //- handle peer disconnect
    case .error(let err):
        //- handle error
    }
}

Clink will automatically handle archival of all paired peers to UserDefaults. Alternatively, you can implement your own storage solution by first creating a custom object that conforms to the ClinkPeerManager protocol:

public protocol ClinkPeerManager {
    func createPeer<T: ClinkPeer>(withId peerId: String) -> T
    func update(value: Any, forKey key: String, ofPeerWithId peerId: String)
    func getPeer<T: ClinkPeer>(withId peerId: String) -> T?
    func getKnownPeers<T: ClinkPeer>() -> [T]
    func delete(peerWithId peerId: String)
}

Then, updating the Clink configuration object to point to it: Clink.Configuration.peerManager = myCustomManager

Just add pod Clink to your Podfile

Nick Sweet, nasweet@gmail.com

Clink is available under the MIT license. See the LICENSE file for more info.