How can I reconnect to device after disconnecting in Core Bluetooth

Question

In Core Bluetooth, after connecting to a device, I turn off the device and the device is disconnected. But when I turn on the device again, there is no didDiscoverPeripher

Answer 1

@Andras gave me the right path, but his answer is not complete anymore since iOS7.

The best way to reconnect to a previous device is to use the retrievePeripherals(withIdentifiers:) method.

This method does not call a delegate, but directly returns you a list of Peripherals, corresponding to the list of UUID passed in parameters.

if let peripheral = self.centralManager.retrievePeripherals(withIdentifiers: [uuid]).first {
    self.peripheral = peripheral // <-- super important
    self.centralManager.connect(peripheral, options: nil)
}

Please check the "super important" line of the above code: The method connect(_:option:) does not retain the peripheral, and if you don't do it yourself, the connection will always fail without any callback since the peripheral objet will be destroyed.