Nearby Bluetooth devices using Swift 3.0

Question

I'm looking for a way to programmatically list any nearby Bluetooth devices (discoverable) that my device finds. I have not been able to find any information or tutorials regarding performing this call in Swift 3.0. This Q-A post discusses finding these devices using Swift 1.0 and building in Xcode 6, rather than the latest version 8.

I did my best to try to make my code into the 3.0 Syntax from the 1.0, but while running the following code, nothing is returned in the Playground:

import Cocoa
import IOBluetooth
import PlaygroundSupport

class BlueDelegate : IOBluetoothDeviceInquiryDelegate {
    func deviceInquiryComplete(_ sender: IOBluetoothDeviceInquiry, error: IOReturn, aborted: Bool) {
        aborted
        print("called")
        let devices = sender.foundDevices()
        for device : Any? in devices! {
            if let thingy = device as? IOBluetoothDevice {
                thingy.getAddress()
            }
        }
    }
}

var delegate = BlueDelegate()
var inquiry = IOBluetoothDeviceInquiry(delegate: delegate)
inquiry?.start()
PlaygroundPage.current.needsIndefiniteExecution = true

Are you failing to see devices that do show up in a nearby iPhone or Mac's Bluetooth panel as discoverable? The Mac doesn't provide a general purpose Bluetooth sniffer. — Rob Napier
So these are all devices that do show up as discoverable by some other nearby device, but the above code doesn't see them? (When you say "after a button is pressed" do you mean "the button that makes the device discoverable" or do you mean "a button in my UI?") — Rob Napier
It doesn't matter if the device doing the search is discoverable. It matters if the devices you want to detect are currently discoverable. You will know this if they show up in other Bluetooth preference panels in iOS or Mac. If they're not showing up there, they're very unlikely to show up here. — Rob Napier
developer.apple.com/videos/play/wwdc2012/703 developer.apple.com/videos/play/wwdc2013/703 This doesn't really lend itself to StackOverflow. Watch the videos, play a little w/ CoreBluetooth, and contact me at [email protected] if you find yourself stuck. Bluetooth is a somewhat complicated beast. — Rob Napier
Thought I'd share that I implemented it properly in my answer below: @RobNapier — Dylan

Dylan Dylan · Accepted Answer · 2017-01-30T17:05:56

Using IOBluetooth the Correct Way

The following code works flawlessly in Xcode Version 8.2.1 (8C1002), Swift 3.0. There are a few lines that aren't required, such as the entire method of deviceInquiryStarted.

Update: These usages still work as of Xcode 9.2 (9B55) and Swift 4.

Playground

import Cocoa
import IOBluetooth
import PlaygroundSupport
class BlueDelegate : IOBluetoothDeviceInquiryDelegate {
    func deviceInquiryStarted(_ sender: IOBluetoothDeviceInquiry) {
        print("Inquiry Started...")
//optional, but can notify you when the inquiry has started.
    }
    func deviceInquiryDeviceFound(_ sender: IOBluetoothDeviceInquiry, device: IOBluetoothDevice) {
        print("\(device.addressString!)")
    }
    func deviceInquiryComplete(_ sender: IOBluetoothDeviceInquiry!, error: IOReturn, aborted: Bool) {
//optional, but can notify you once the inquiry is completed.
    }
}
var delegate = BlueDelegate()
var ibdi = IOBluetoothDeviceInquiry(delegate: delegate)
ibdi?.updateNewDeviceNames = true
ibdi?.start()
PlaygroundPage.current.needsIndefiniteExecution = true

Project-Application Usage

import Cocoa
import IOBluetooth
import ...
class BlueDelegate : IOBluetoothDeviceInquiryDelegate {
    func deviceInquiryStarted(_ sender: IOBluetoothDeviceInquiry) {
        print("Inquiry Started...")
}
    func deviceInquiryDeviceFound(_ sender: IOBluetoothDeviceInquiry, device: IOBluetoothDevice) {
        print("\(device.addressString!)")
    }
}

//other classes here:



//reference the following outside of any class:
var delegate = BlueDelegate()
var ibdi = IOBluetoothDeviceInquiry(delegate: delegate)

//refer to these specifically inside of any class:
ibdi?.updateNewDeviceNames = true
ibdi?.start() //recommended under after an action-button press.

Explanation

The issue I was originally faced with was trying to access the information as the inquiry was still in process.

When I accessed it, under many different occasions my playground would hang and I would be forced to force quit both Xcode.app, and com.apple.CoreSimulator.CoreSimulatorService from the Activity Monitor. I lead myself to believe that this was just a Playground bug, only to learn that my application would crash once the inquiry finished.

As Apple's API Reference states:

Important Note: DO NOT perform remote name requests on devices from delegate methods or while this object is in use. If you wish to do your own remote name requests on devices, do them after you have stopped this object. If you do not heed this warning, you could potentially deadlock your process.

Which entirely explained my issue. Rather than directly asking for the IOBluetoothDevice information from the sender.foundDevices() method (which I believe may not have been updating..?) I simply used the parameters built into the function to mention that it was indeed an IOBluetoothDevice object, and simply to ask for that information to be printed.

Final Note

I hope that this Q/A I've created helps others in need when using IOBluetooth in Swift. The lack of any tutorials and the high amounts of outdated, Objective-C code made finding this information very challenging. I'd like to thank @RobNapier for the support on trying to find the answer to this riddle in the beginning. I'd also like to thank NotMyName for the reply on my post on the Apple Developer Forums.

I will be exploring the usage of this in an iOS device more sooner than later!