Polling for Response from BLE Adapter in Swift

Question

Using a Wi-Fi socket based adapter, I can successfully poll for a response like so:

    func writeMessageWithResponse(message: String) -> [String] {
        self.waitingForResponse = true
        let runLoop = NSRunLoop.currentRunLoop()
        if self.response != nil {
            self.response?.removeAll()
        }

        writeMessage(message) // this will set self.waitingForResponse to false when a response is received

        while self.waitingForResponse && runLoop.runMode(NSDefaultRunLoopMode, beforeDate: NSDate.distantFuture()) {
             // waiting for flag (self.waitingForResponse) to be set
        }

        return self.response!
    }

When I use this same code with a CBCentralManager BLE connection, the main thread is blocked and does not receive the response from the connection. I've tried changing the CBCentralManager to a different queue, but I get the same results.

Does anybody have an idea how to wait in a loop and still be able to receive a BLE response? I know a response is being sent, but the thread is blocked and not reading it.

Using an async function with a completionHandler won't work for this use case because I need a reusable function that can issue a chain of commands that each depend on the result of the last response.

Answer 1

The CBCentralManager and CBPeripheral APIs are not really designed for this. You should be using the methods provided by CBPeripheralDelegate and CBCentralManagerDelegate protocols. Initialize your central manager with a dedicated queue so that you can listen for responses to your peripherals and act on that data as appropriate.