Swift 5.7: Trouble Managing State in a Multipeer Connectivity Session When Disconnected
I'm having trouble with I'm trying to configure I've been struggling with this for a few days now and could really use some help. I'm sure I'm missing something obvious here, but I'm working on a personal project and I'm working on a personal project and I'm currently working on an iOS app that utilizes Multipeer Connectivity to connect multiple devices for a collaborative drawing feature... The challenge I'm facing is how to effectively manage the app's state when a peer unexpectedly disconnects from the session. I need to handle the disconnection gracefully without losing the current drawing state. When a peer disconnects, I receive the `peerDidChangeState` callback, but I'm unsure how to update my UI and manage my data model accordingly. Here's a snippet of the relevant code where I handle the state change: ```swift func session(_ session: MCSession, peer peerID: MCPeerID, didChange state: MCSessionState) { switch state { case .connected: print("Connected to \(peerID.displayName)") case .connecting: print("Connecting to \(peerID.displayName)") case .notConnected: print("Disconnected from \(peerID.displayName)") // Here I want to update the UI and potentially save the drawing state handleDisconnection(for: peerID) } } ``` When a peer disconnects, I attempt to call `handleDisconnection(for: peerID)`, but I'm facing an issue where the app sometimes crashes with a `fatal error: Index out of range` when I try to remove the disconnected peer from my drawing model. My drawing model is an array of `Drawing` objects that keeps track of each peer's strokes. I suspect that there might be a race condition or an issue with the way I'm mutating the state. I've tried wrapping the UI updates and model mutations in a `DispatchQueue.main.async` block, but it hasn't resolved the issue. Also, I implemented a guard clause to check if the peer ID exists in my model before attempting to remove it: ```swift func handleDisconnection(for peerID: MCPeerID) { guard let index = drawings.firstIndex(where: { $0.peerID == peerID }) else { return } drawings.remove(at: index) } ``` However, this still leads to crashes if multiple disconnections happen simultaneously. Any advice on how I can better manage the state of my app during these disconnections would be greatly appreciated! Are there best practices for handling state in a Multipeer Connectivity session, especially regarding UI updates and data integrity? Is there a better approach? For context: I'm using Swift on macOS. What's the best practice here? What are your experiences with this? I'd really appreciate any guidance on this. I'd be grateful for any help. This is happening in both development and production on Ubuntu 22.04. Any feedback is welcome!