iOS BLE CentralManager didFailToConnect to peripheral not being called - ios

Question

In the case where a peripheral has been discovered by a central, but right before user presses a button to connect, the peripheral goes out of range, so the connection cannot be completed. What method is called by CoreBluetooth?
I thought that centralManager didFailToConnect would be called, but in my code it is not being called, perhaps because the connection never started at all?
In this scenario which method should I use.
Thanks in advance for any help.
public func centralManager(_ central: CBCentralManager, didFailToConnect peripheral: CBPeripheral, error: Error?) {
print("[ERROR] Could not connect to peripheral \(peripheral.identifier.uuidString) error: \(error!.localizedDescription)")
}

Answer 1

As said in the previous answer, none of the delegate methods will be called if any device does not initiated the connecting process.didFailToConnect method only invoked if the device initiated a connection procedure but due to any reason that device could not able to connect.
If you want to check if any device is there for the connection, then you need to create one timer for the specific time period and if during that period if no device is scanned then you can show a message showing "no device available" and again check for devices.

Answer 2

Nothing will be called in this scenario since the peripheral was not connected, nor was there an error connecting to the peripheral.
Core Bluetooth will have a pending connection for that peripheral and once it comes back into range the connection will complete and didConnectPeripheral will be called.

Answer 3

I faced a similar case,
What I needed was to handle a scenario where the user already had the device discovered but has waited some time before trying to connect and the device might not be available to connect anymore.
I didn't need any complex solution to maintain the In-Range status for the device just a solution that would recheck if the previously discovered device is still in-range without actually needing to maintain any status.
I solved it using below method:
I created a timeout logic of around 5 seconds (which we will invalidate if the connection was successful before the timeout) along with the connection request action.
If the connection was not made within 5 seconds, the timeout block will execute the disconnection request on the previously discovered peripheral which will cause the didFail delegate to be called by the central manager.
Timer.scheduledTimer(withTimeInterval: 5, repeats: false, block: { timer in
DEVICE_SCANNER_MANAGER.disconnectPeripheral()
DispatchQueue.main.async {
Utility.showAlert(vc: self, title: "", msg: "device went out of range", btnPrimary: "OK", handler: nil)
}
})
DEVICE_SCANNER_MANAGER => Custom manager class to handle all peripheral related operations.