Average Happiness is a single view application that allows the user to calculate their average happiness. Users can also toggle on and off which entries are included in the calculation.

Our custom cell with contain the UI elements of our UITableViewCell and update the data within them

1. Create a new Cocoa Touch Class called EntryTableViewCell that is a subclass of UITableViewCell
2. Delete all existing functions within our new cell class
3. Drag out outlets for all UI elements on our tableview cell
   • be sure to subclass our Cell as type EntryTableViewCell

@IBOutlet weak var titleLabel: UILabel!
@IBOutlet weak var higherorLowerLabel: UILabel!
@IBOutlet weak var isEnabledSwitch: UISwitch!

4. Create a variable called entry of an optional type Entry var entry: Entry?

5. Create a function called updateUI that takes in an Int. This will update the UI Elements on our UITableViewCell. Note that we are not setting our higherorLowerLabel yet as we don’t have a function to detect what it should be set too. We are building that next.

func updateUI(averageHappiness: Int) {
    guard let entry = entry else {return}
    titleLabel.text = “\(entry.title) -> \(entry.happiness)”
    isEnabledSwitch.isOn = entry.isIncluded
    higherorLowerLabel.text = entry.happiness >= averageHappiness ? “Higher” : “Lower”
}

1. Create a new Cocoa Touch Classcalled EntryListTableViewController
   • be sure to subclass our TableView as type EntryListTableViewController
2. Remove all functions except
   • ViewDidLoad
   • numberOfRowsInSection
   • cellForRowAt
3. Create a variable called averageHappiness of type Int, give it a preset value of 0
4. In our numberOfRowsInSection return EntryController.entries.count
5. In our cellForRowAt guard let our cell to be of type EntryTableViewCell guard let cell = tableView.dequeueReusableCell(withIdentifier: “EntryCell”, for: indexPath) as? EntryTableViewCell else {return UITableViewCell()}
6. Pass an entry to our cell then update the UI

///grabbing the entry that we want
let entry = EntryController.entries[indexPath.row]
///passing our entry to out function setEntry
cell.entry = entry
///Updating the UI or our cell
cell.updateUI(averageHappiness: averageHappiness)

Explain Protocols and Delegates Analogy that you can use * Intern * Has a list of stuff that the boss might want done and can tells the workers to do it * Boss * Tells his intern what he wants done and might give some information for the intern to pass on, (ex: and Int of bool) * Worker * Is prepared to do anything the boss might want to do * Gets told by the intern when to do a certain task

1. Back on our EntryTableViewCell declare a new protocol called EntryCellDelegate of type class above our EntryTableViewCell class
2. Inside our protocol declare a function called switchToggled that takes in a EntrytableViewCell
3. Inside our EntryTableViewCell class create a new property called delegate of type EntryCellDelegate?
4. Create an IBActionfor the UISwitch with a sender of UISwitch
5. Inside the UIAction call our delegates switchToggled function passing in self
6. Back on our EntryListTableViewController create an extension of type EntryCellDelegate and conform to all protocols.
7. Inside of our newly made switchToggled function add a print statement for that says “switchToggled” for testing purposes
8. In our CellForRowAt add cell.delegate = self before we return the cell
9. Run the app and make sure that “switchToggled” is being printed
10. Create a new function in our EntryListTableViewController called updateHappiness that recalculates the average happiness

func updateHappiness() {
    var happinessTotal = 0
    //loops through all of our entries
    for entry in EntryController.entries {
        //If our entrys isIncluded is == true, then we add its happiness to happiness total
        if entry.isIncluded {
            happinessTotal += entry.happiness
        }
    }
    //calculates our average happienss
    averageHappiness = happinessTotal / EntryController.entries.filter({$0.isIncluded}).count
}

12. Back inside our switchToggled function we need to update our update our cells info and our average Happiness, run the app

guard let indexPath = tableView.indexPath(for: cell) else {return}
let entry = EntryController.entries[indexPath.row]
EntryController.updateEntry(entry: entry)
updateHappiness()

Note: Explain Notifications and Observers, Analogy that you can use * Notifications are like a radio tower, and observers are like a radio, observers can only hear the station that they are tuned into

1. Create a new .swift file called NotificationKeys in our Resources folder
2. Inside of our NotificationKeys create a struct called Constants the contains a static property called notificationKey. Set it equal to Notification.Name(rawValue: “didChangeHappiness”)
3. On our averageHappiness add a didSet that septs our a notification every time we update the variable. For the object pass averagehappiness. Also set our title to the average happiness so we can see what it is in the application

var averageHappiness: Int = 0 {
    /*
     Everytime that we set out happiness level we post a notification that contains our notificationKey and our averageHappiness
     */
    didSet {
        NotificationCenter.default.post(name: Constants.notificationKey, object: averageHappiness)
        self.title = "Average Happiness: \(averageHappiness)"
    }
}

3. On our EntryTableViewCell create a function called addObserver that adds an observer listening for our notificationKey

func createObserver() {
    NotificationCenter.default.addObserver(self, selector:
#selector(self.recalcHappiness), name: Constants.notificationKey, object: nil)
}

5. Next add an objC function called recalcHappiness that updates our cells average happiness label

@objc func recalcHappiness(notification: NSNotification) {
    guard let averageHappiness = notification.object as? Int, let entry = entry else {return}
      higherOrLowerLabel.text = entry.happiness >= averageHappiness ? “Higher” : “Lower”
}