How to wait until delegate method is called? - ios

Question

I want to create a method startCentralManager that waits until the delegate method centralManagerDidUpdateState is called and returns a boolean value depending on the central state.
I want to use the method like this:
let centralManager = CentralManager()
let ready = centralManager.startCentralManager()
The CentralManager class should look something like this
class CentralManager: NSObject, CBCentralManagerDelegate {
var centralManager: CBCentralManager?
func startCentralManager() -> Bool {
centralManager = CBCentralManager.init(delegate: self, queue: nil)
}
func centralManagerDidUpdateState(central: CBCentralManager) {
// startCentralManager() should return this
return central.state == CBCentralManagerState.PoweredOn
}
}
How can I solve this?
Thank you very much, in advance.
UPDATE:
There are some other methods, but the situation is almost equal. Another method is the following:
let connected = centralManager.connect<PARAMS>)
In this method if have to call
func scanForPeripheralsWithServices(_ serviceUUIDs: [CBUUID]?, options options: [String : AnyObject]?)
and wait until the delegate method
func centralManager(_ central: CBCentralManager, didDiscoverPeripheral peripheral: CBPeripheral, advertisementData advertisementData: [String : AnyObject], RSSI RSSI: NSNumber)
is called. Here, I have to call
func connectPeripheral(_ peripheral: CBPeripheral, options options: [String : AnyObject]?)
and again wait until the delegate method
func centralManager(_ central: CBCentralManager, didConnectPeripheral peripheral: CBPeripheral)
is called. In case of success, the call to centralManager.connect(<PARAMS>) should return true.

Answer 1

CBCentralManager works asychronously and you get informed of its status through a call to your delegate at some point in time that you have no direct control over.
You can't wait for asynchronous response between two lines of code. You'll have to design your program differently.
If you have a view controller that depends on the readiness of the CBCentralManager, you can make it the delegate and enable its peripheral related controls when your centralManagerDidUpdateState function is called.
for example (if you're using this for a scanner) :
class ScanningViewController:UIViewController,CBCentralManagerDelegate
{
var centralManager: CBCentralManager? = nil
override viewDidLoad()
{
centralManager = CBCentralManager.init(delegate: self, queue: nil)
}
func centralManagerDidUpdateState(central: CBCentralManager)
{
if central.state == CBCentralManagerState.PoweredOn
{
// enable scanning controls here
}
}
}

Answer 2

I found a solution:
class CentralManager: NSObject, CBCentralManagerDelegate {
var centralManager: CBCentralManager?
var ready: Bool = false
func startCentralManager() -> Bool {
centralManager = CBCentralManager.init(delegate: self, queue: nil)
ready = false
while ready == false {
NSRunLoop.currentRunLoop().runMode(NSDefaultRunLoopMode, beforeDate: NSDate.distantFuture())
}
return ready
}
func centralManagerDidUpdateState(central: CBCentralManager) {
ready = central.state == CBCentralManagerState.PoweredOn
}
}
Is this a good programming practice? Is there a better solution?
Thank you.

Answer 3

Create a timer that fires every X seconds
Inside the timer's selector check if connected and invalidate the timer or let it keep checking if not connected
Or consider using a semaphore and a dispatch_wait_forever