interaction-app.md

Interactivity between an iPhone & Apple Watch

Now that we've build a few stand alone apps for both the iPhone and Apple Watch,
It's time to build 👷‍ something that will work on both devices!

Our first step would be to go about understanding how to connect iPhone to an Apple
Watch, enter:

WatchConnectivity Framework

Used to connect and relay messages in both directions between the two devices

We'll be using the classes and protocol provided by this framework to create a connection in our app.

Setup

Project

Create a Project (iOS App with WatchKit App)

Watch

Create a Button (style it as you wish) and connect it to the controller as an action

@IBAction func buttonClicked() {
    print("Button Clicked!")
}

Next we need to use the WatchConnectivity framework to setup the Watch to be able to send and receive requests from the phone.

Firstly lets import WatchConnectivity and require it in the controller class

import WatchConnectivity

class InterfaceController: WKInterfaceController, WCSessionDelegate {

public func session(_ session: WCSession, activationDidCompleteWith
  activationState: WCSessionActivationState, error: Error?) {
  // leave empty
 }

 //rest of code
}

As you can see above, we have a required method called activationDidCompleteWith:error, This is called when the activation of a method finishes

Next lets activate and initialise the WCSession that will establish a connection between the two devices

// if WCSession is supported then create a default session
fileprivate let session: WCSession? = WCSession.isSupported() ? WCSession.default() : nil

// activate the optional session?
override init() {
    super.init()

    session?.delegate = self
    session?.activate()
}

Lets send the message off to the phone, to do so, we need to go back to the buttonClick action and send the message. sendMessage is one of the ways to transfer information from the watch to the phone

// INSIDE buttonClick Action
let applicationData = ["counterValue" : 1]

// The paired iPhone has to be connected via Bluetooth.
if let session = session, session.isReachable {
    session.sendMessage(applicationData,
                        replyHandler: { replyData in
                            // handle reply from iPhone app here
                            print(replyData)
    }, errorHandler: { error in
        // catch any errors here
        print(error)
    })
} else {
    // when the iPhone is not connected via Bluetooth
}

Phone

The setup on the watch is pretty much complete, so lets move onto the phone.

Create some Labels and a button, also connect the button and one of the labels up to the controller so that if a user touches the button, then the text on the label will change to phone click

I've connected up my button and the label that says "No"

@IBOutlet weak var clickedLabel: UILabel!

@IBAction func phoneButtonClicked(_ sender: UIButton) {
     self.clickedLabel.text = "Phone Click"
     print("clicked on Phone")

 }

Now lets create the WCSession on the watch so that the two devices can interact with each other

import WatchConnectivity

class ViewController: UIViewController, WCSessionDelegate {

  public func sessionDidDeactivate(_ session: WCSession) {
      // Code
  }
  public func sessionDidBecomeInactive(_ session: WCSession) {
      // Code
  }
  public func session(_ session: WCSession, activationDidCompleteWith activationState: WCSessionActivationState, error: Error?) {
      // Dummy Implementation
  }

  // if WCSession is supported then create a default session
  fileprivate let session: WCSession? = WCSession.isSupported() ? WCSession.default() : nil

  // activate the optional session?
  required init?(coder aDecoder: NSCoder) {
      super.init(coder: aDecoder)

      session?.delegate = self
      session?.activate()
  }

//Rest of the code
}

You'll notice a couple more required methods in the phones controller.

Now lets write the method that will receive the message that has been sent by the Watch

func session(_ session: WCSession, didReceiveMessage message: [String : Any], replyHandler: @escaping ([String : Any]) -> Void) {

    DispatchQueue.main.async {
        print("Yes")
        self.clickedLabel.text = "Watch Click"
    }
}

And that should be it! If we run the simulator for both the iPhone and Apple Watch, you should be able to see it all working as expected.

---

Hint
If you are unable to get both the simulators working then Change the active scheme from just app to apple watch app + phone app as seen below
Hint