watchkit

WatchConnectivity

Introduction#

Connecting your WatchOS application to your iOS application can be a task to complete when you have never done it before. This tutorial will show you the basic fundamentals in order to accomplish this very important task.

iOS Configuration

iPhone App

  1. import WatchConnectivity and conform to WCSessionDelegate.
  2. use the static session delegate via WCSession.default().
  3. Send data to Watch app using:
 WCSession.default().sendMessage(message, replyHandler:_ errorHandler:_)
  1. The message object should be a dictionary of type [String:Any]
  2. If you are looking for data to be returned from the Watch app, provide the logic in a closure defined in the replyHandler; otherwise, pass in nil.
  3. To respond to messages sent from the Watch app, you will use the WCSessionDelegate callback method
func session(_ session: WCSession, didReceiveMessage message: [String : Any], replyHandler: @escaping ([String : Any]) -> Swift.Void){...}

You need to import the WatchConnectivity framework into your view controller file in the iOS application. This gives you access to the class objects that are designed to communicate with the Watch companion application. You will need to import this on the Watch app side as well. The only real difference with the Watch app is that you will not have a view controller file, but an interface controller file.

import WatchConnectivity

Next, you will need to make sure that your application can support a session for WatchConnectivity. If it can, then you must set the view controller as its delegate and activate the default session. You will get an error here. You need to conform to WCSessionDelegate and implement a few methods before the IDE begins to calm down.

// MARK: - View Life Cycle Callbacks
override func viewDidLoad() {
    super.viewDidLoad()

    automaticallyAdjustsScrollViewInsets = false
    if WCSession.isSupported() {
        WCSession.default().delegate = self
        WCSession.default().activate()
    }
    else {
        print("\nViewController: connectionManager is nil\n")
    }
}

To conform to WCSessionDelegate, let’s add an extension to the bottom of the view controller. Some people hate this approach. I have my way, but for tutorial purposes, I will follow the RayWenderlich approach. I am a huge fan of just getting code directly from COMMAND + CLICKING on the delegates and grabbing ALL OF THE METHODS out of the specification and begin to manipulate it and understand how things work. In this extension, I am providing you will all of the methods. They are already marked so that you will see when each of them fire in the console. If you feel frisky, delete some of the ones that are marked OPTIONAL to make your code file look spiffy.

extension ViewController : WCSessionDelegate {

    func session(_ session: WCSession, activationDidCompleteWith activationState: WCSessionActivationState, error: Error?) {
        print("0. ViewController: ", "activationDidCompleteWith activationState")
    }


    /** ------------------------- iOS App State For Watch ------------------------ */

    func sessionDidBecomeInactive(_ session: WCSession) {
        print("1. ViewController: ", "sessionDidBecomeInactive")
    }


    func sessionDidDeactivate(_ session: WCSession) {
        print("2. ViewController: ", "sessionDidDeactivate")
    }


    func sessionWatchStateDidChange(_ session: WCSession) {
        print("3. ViewController: ", "sessionDidDeactivate")
    }


    /** ------------------------- Interactive Messaging ------------------------- */

    func sessionReachabilityDidChange(_ session: WCSession) {
        print("4. ViewController: ", "sessionReachabilityDidChange")
    }


    func session(_ session: WCSession, didReceiveMessage message: [String : Any]) {
        print("5. ViewController: ", "didReceiveMessage")
    }



    func session(_ session: WCSession, didReceiveMessage message: [String : Any], replyHandler: @escaping ([String : Any]) -> Swift.Void) {
        print("6. ViewController: ", "didReceiveMessage")
        // This is where you handle any requests coming from your Watch App
    }

    func session(_ session: WCSession, didReceiveMessageData messageData: Data) {
        print("7. ViewController: ", "didReceiveMessageData")
    }

    func session(_ session: WCSession, didReceiveMessageData messageData: Data, replyHandler: @escaping (Data) -> Swift.Void) {
        print("8. ViewController: ", "didReceiveMessageData")
    }

    /** -------------------------- Background Transfers ------------------------- */

    func session(_ session: WCSession, didReceiveApplicationContext applicationContext: [String : Any]) {
        print("9. ViewController: ", "didReceiveApplicationContext")
    }

    func session(_ session: WCSession, didFinish userInfoTransfer: WCSessionUserInfoTransfer, error: Error?) {
        print("10. ViewController: ", "didFinish userInfoTransfer")
    }

    func session(_ session: WCSession, didReceiveUserInfo userInfo: [String : Any] = [:]) {
        print("11. ViewController: ", "didReceiveUserInfo")
    }

    func session(_ session: WCSession, didFinish fileTransfer: WCSessionFileTransfer, error: Error?) {
        print("12. ViewController: ", "didFinish fileTransfer")
    }

    func session(_ session: WCSession, didReceive file: WCSessionFile) {
        print("13. ViewController: ", "didReceive file")
    }
}

To send data to your Watch App, once the Watch App has requested it, you will handle this in the method…

func session(_ session: WCSession, didReceiveMessage message: [String : Any], replyHandler: @escaping ([String : Any]) -> Swift.Void) {
    print("6. ViewController: ", "didReceiveMessage")
    // build out your response message using a Dictionary
    let returnMessage: [String : Any] = [
       "key1" : value1,
       "key2" : value2,
       "key3" : value3
    ]
    // return your data in this manner
    replyHandler(returnMessage)
    // WARNING
    // You must call the replyHandler before the method ends, otherwise, your app will crash.
}

This is only one half of the transaction! You must configure your Watch app to connect to the iPhone app and handle any returned messages!

Watch Extension Configuration

WatchKit App

  1. import WatchConnectivity and conform to WCSessionDelegate.
  2. use the static session delegate via WCSession.default().
  3. Send data to the iPhone app using:
 WCSession.default().sendMessage(message, replyHandler:_ errorHandler:_)
  1. The message object should be a dictionary of type [String:Any]
  2. If you are looking for data to be returned from the Watch app, provide the logic in a closure defined in the replyHandler; otherwise, pass in nil.
  3. To respond to messages sent from the iPhone app, you will use the WCSessionDelegate callback method
func session(_ session: WCSession, didReceiveMessage message: [String : Any], replyHandler: @escaping ([String : Any]) -> Swift.Void){...}
  1. These methods will not be required in your Watch app to properly conform to the WCSessionDelegate:
 func sessionDidBecomeInactive(_ session: WCSession)
 func sessionDidDeactivate(_ session: WCSession)
 func sessionWatchStateDidChange(_ session: WCSession)

And finally, it is generally best practice to store any common images, the images and assets that will continually be used for the Watch app to be placed in the Watch’s xcassets folder. Okay, now that you are confused, let’s get to the details!

It might be a surprise to you, but you need to import WatchConnectivity again.

import WatchConnectivity

Next, you need to verify that the session is even possible.

// MARK: - View Life Cycle Callbacks
override func awake(withContext context: Any?) {
    super.awake(withContext: context)

    // Configure interface objects here.
    if WCSession.isSupported() {
        WCSession.default().delegate = self
        WCSession.default().activate()
        print("InterfaceController: Session Activated")

        // Request Data from iPhone App
        let requestMessage = ["message":"get-data"]

        WCSession.default().sendMessage(requestMessage, replyHandler: { (replyMessage) in
            print("Got a reply from the phone: \(replyMessage)")

            // handle reply message here

        }, errorHandler: { (error) in
            print("Got an error sending to the phone: \(error)")
        })
    }
    else {
        print("\nViewController: connectionManager is nil\n")
    }
}

But none of this will work, unless you implement methods required for the WCSessionDelegate.

extension InterfaceController : WCSessionDelegate {

    func session(_ session: WCSession, activationDidCompleteWith activationState: WCSessionActivationState, error: Error?) {
        print("1. InterfaceController: ", "activationDidCompleteWith activationState") // first
    }

    /** ------------------------- Interactive Messaging ------------------------- */

    func sessionReachabilityDidChange(_ session: WCSession) {
        print("2. InterfaceController: ", "sessionReachabilityDidChange") // second
    }

    func session(_ session: WCSession, didReceiveMessage message: [String : Any]) {
        print("3. InterfaceController: ", "didReceiveMessage")
    }

    func session(_ session: WCSession, didReceiveMessage message: [String : Any], replyHandler: @escaping ([String : Any]) -> Swift.Void) { // third
        print("4. InterfaceController: ", "didReceiveMessage")
        //print("Message Contents: ", message["message"]!)
    }

    func session(_ session: WCSession, didReceiveMessageData messageData: Data) {
        print("5. InterfaceController: ", "didReceiveMessageData")
    }

    func session(_ session: WCSession, didReceiveMessageData messageData: Data, replyHandler: @escaping (Data) -> Swift.Void) {
        print("6. InterfaceController: ", "didReceiveMessageData")
    }

    /** -------------------------- Background Transfers ------------------------- */

    func session(_ session: WCSession, didReceiveApplicationContext applicationContext: [String : Any]) {
        print("7. InterfaceController: ", "didReceiveApplicationContext")
    }

    func session(_ session: WCSession, didFinish userInfoTransfer: WCSessionUserInfoTransfer, error: Error?) {
        print("8. InterfaceController: ", "didFinish userInfoTransfer")
    }

    func session(_ session: WCSession, didReceiveUserInfo userInfo: [String : Any] = [:]) {
        print("9. InterfaceController: ", "didReceiveUserInfo")
    }

    func session(_ session: WCSession, didFinish fileTransfer: WCSessionFileTransfer, error: Error?) {
        print("10. InterfaceController: ", "didFinish fileTransfer")
    }

    func session(_ session: WCSession, didReceive file: WCSessionFile) {
        print("11. InterfaceController: ", "didReceive file")
    }    
}

Sending Data

Sending data to your Watch app from your iPhone or from your iPhone to your Watch App after triggering some event is very simple, though the code can look a little complex at first.

let message = ["key":"value-to-send"]

WCSession.default().sendMessage(message, replyHandler: { (replyMessage) in
    print("Got a reply from the phone: \(replyMessage)")

    if let returnedValues = replyMessage["returned-value"] as? NSArray {
        for val in returnedValues {
            // do something here with the data
            // Dispatch to Main Thread if affecting UI
        }
    }
}, errorHandler: { (error) in
    print("Got an error sending to the phone: \(error)")
})
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