1.4 Zoo Learning Activity

Prepare Your Working Copy

The Goal

Protect your completed 1.3 checkpoint and begin 1.4 from a separate working copy.

Your Task

1. Back up your completed Zoo 1.3 LastName folder.
2. Copy the folder and rename the working copy Zoo 1.4 LastName.
3. Rename the solution file to Zoo 1.4 LastName.sln.
4. Open the copied solution and build it before editing.

Understand the Change

The Goal

Make existing methods flexible by passing information into them through parameters.

What This Means

In 1.3, several methods used fixed values inside the method body. For example, an animal always gained the same amount of weight and a ticket sale always represented one ticket. In 1.4, the caller supplies those amounts when it calls the method.

A parameter is a named input in a method declaration. An argument is the actual value supplied in the method call. The method can then use the received value in its calculation.

Pass Values into Animal-Care Methods

The Goal

Replace fixed amounts with parameters in the animal, birthing-room, vending-machine, and wallet behaviors.

Update ZooScenario/Business Classes/Animal.cs

Replace the existing Eat method. The method now receives both changes and applies each one only when it is positive.

public void Eat(double weightGain, int happinessGain)
{
    if (weightGain > 0)
    {
        this.Weight = this.Weight + weightGain;
    }

    if (happinessGain > 0)
    {
        this.HappinessLevel = this.HappinessLevel + happinessGain;
    }
}

Update ZooScenario/Business Classes/BirthingRoom.cs

Add WarmRoom, then replace WakeMotherUp. The temperature increase is passed from one method to the next.

public void WarmRoom(double temperatureIncrease)
{
    if (temperatureIncrease > 0)
    {
        this.Temperature = this.Temperature + temperatureIncrease;
    }
}

public void WakeMotherUp(double temperatureIncrease)
{
    this.Mother.WakeUp();
    this.WarmRoom(temperatureIncrease);
}

Update ZooScenario/Business Classes/VendingMachine.cs

Replace these three methods so the caller controls bag sizes and the money amount.

public void AddFoodBag(double poundsOfFood)
{
    if (poundsOfFood > 0)
    {
        this.FoodStock = this.FoodStock + poundsOfFood;
    }
}

public void FillVendingMachine(double firstBagPounds, double secondBagPounds)
{
    this.AddFoodBag(firstBagPounds);
    this.AddFoodBag(secondBagPounds);
}

public void AddMoney(decimal moneyAmount)
{
    if (moneyAmount > 0)
    {
        this.MoneyBalance = this.MoneyBalance + moneyAmount;
    }
}

Update ZooScenario/Business Classes/Wallet.cs

Replace these methods so the wallet can add a supplied amount and subtract the price of multiple tickets.

public void AddMoney(decimal moneyAmount)
{
    if (moneyAmount > 0)
    {
        this.MoneyBalance = this.MoneyBalance + moneyAmount;
    }
}

public void RemoveTicketPrice(decimal ticketPrice, int ticketCount)
{
    if (ticketPrice > 0)
    {
        if (ticketCount > 0)
        {
            decimal totalTicketPrice = ticketPrice * ticketCount;
            this.MoneyBalance = this.MoneyBalance - totalTicketPrice;
        }
    }
}

Pass Ticket Information Through the Object Model

The Goal

Let one ticket count move through the guest, wallet, booth, and employee objects so every related object updates consistently.

Update ZooScenario/Business Classes/Guest.cs

Replace BuyTicket and VisitZoo. The guest passes the ticket price and count to the wallet.

public void BuyTicket(decimal ticketPrice, int ticketCount)
{
    this.Wallet.RemoveTicketPrice(ticketPrice, ticketCount);
}

public void VisitZoo(decimal ticketPrice, int ticketCount)
{
    this.BuyTicket(ticketPrice, ticketCount);
}

Update ZooScenario/Business Classes/Employee.cs

Replace SellTicket. The employee now records the number of tickets sold instead of always adding one.

public void SellTicket(int ticketCount)
{
    if (ticketCount > 0)
    {
        this.TicketsSold = this.TicketsSold + ticketCount;
    }
}

Update ZooScenario/Business Classes/Booth.cs

Replace SellTicket. The booth calculates the total sale, updates its balance, and passes the count to the attendant.

public void SellTicket(int ticketCount)
{
    if (ticketCount > 0)
    {
        decimal totalTicketPrice = this.TicketPrice * ticketCount;
        this.MoneyBalance = this.MoneyBalance + totalTicketPrice;
        this.Attendant.SellTicket(ticketCount);
    }
}

Connect the Values in Zoo.cs

The Goal

Update the coordinating methods in Zoo so each value is passed to the object that needs it.

Your Task

In ZooScenario/Business Classes/Zoo.cs, replace these methods. Keep the methods near their current locations.

public void OpenForVisitor(int ticketCount)
{
    this.SellTicket(ticketCount);
    this.FeaturedAnimal.WakeUp();
}

public void SellTicket(int ticketCount)
{
    if (ticketCount > 0)
    {
        this.Visitor.BuyTicket(this.TicketBooth.TicketPrice, ticketCount);
        this.TicketBooth.SellTicket(ticketCount);
    }
}

public void FeedFeaturedAnimal(
    double weightGain,
    int happinessGain,
    decimal moneyAmount)
{
    this.FeaturedAnimal.Eat(weightGain, happinessGain);
    this.AnimalSnackMachine.AddMoney(moneyAmount);
}

public void PrepareBirthingRoom(double temperatureIncrease)
{
    this.BirthArea.WakeMotherUp(temperatureIncrease);
}

public void FillAnimalSnackMachine(
    double firstBagPounds,
    double secondBagPounds)
{
    this.AnimalSnackMachine.FillVendingMachine(
        firstBagPounds,
        secondBagPounds);
}

Supply Values from MainWindow

The Goal

Give each zoo action the values it should use when the user clicks a button.

Your Task

In ZooScenario/MainWindow.xaml.cs, replace the eight event handlers below. The event handlers now provide arguments to the updated Zoo methods.

private void openComoZooButton_Click(object sender, RoutedEventArgs e)
{
    this.ComoZoo.OpenForVisitor(1);
    this.informationTextBox.Text =
        "The Como Zoo is open for " + this.ComoZoo.Visitor.Name + ".";
}

private void feedComoAnimalButton_Click(object sender, RoutedEventArgs e)
{
    this.ComoZoo.FeedFeaturedAnimal(0.75, 3, 4.25m);
    this.informationTextBox.Text =
        this.ComoZoo.FeaturedAnimal.Name + " has been fed.";
}

private void prepareComoBirthingRoomButton_Click(
    object sender,
    RoutedEventArgs e)
{
    this.ComoZoo.PrepareBirthingRoom(1.5);
    this.informationTextBox.Text =
        "The Como Zoo birthing room is ready.";
}

private void fillComoVendingMachineButton_Click(
    object sender,
    RoutedEventArgs e)
{
    this.ComoZoo.FillAnimalSnackMachine(40.0, 35.0);
    this.informationTextBox.Text =
        "The Como Zoo animal snack machine has been filled.";
}

private void openSanDiegoZooButton_Click(object sender, RoutedEventArgs e)
{
    this.SanDiegoZoo.OpenForVisitor(2);
    this.informationTextBox.Text =
        "The San Diego Zoo is open for " + this.SanDiegoZoo.Visitor.Name + ".";
}

private void feedSanDiegoAnimalButton_Click(
    object sender,
    RoutedEventArgs e)
{
    this.SanDiegoZoo.FeedFeaturedAnimal(0.25, 2, 2.50m);
    this.informationTextBox.Text =
        this.SanDiegoZoo.FeaturedAnimal.Name + " has been fed.";
}

private void prepareSanDiegoBirthingRoomButton_Click(
    object sender,
    RoutedEventArgs e)
{
    this.SanDiegoZoo.PrepareBirthingRoom(0.75);
    this.informationTextBox.Text =
        "The San Diego Zoo birthing room is ready.";
}

private void fillSanDiegoVendingMachineButton_Click(
    object sender,
    RoutedEventArgs e)
{
    this.SanDiegoZoo.FillAnimalSnackMachine(25.0, 25.0);
    this.informationTextBox.Text =
        "The San Diego Zoo animal snack machine has been filled.";
}

Check Your Work

Build First

1. Save all files and build the solution.
2. If a call is underlined, compare its argument count, order, and types with the method declaration.

Trace a Ticket Sale

In ZooScenario/Business Classes/Zoo.cs, place a breakpoint on the first line inside SellTicket(int ticketCount).

1. Press F5 and open the Como Zoo.
2. Confirm ticketCount is 1.
3. Use F10 to step through the calls and observe the wallet, booth, and employee values change.

Trace an Animal Feeding

In ZooScenario/Business Classes/Animal.cs, place a breakpoint on the first if statement inside Eat(double weightGain, int happinessGain).

1. Press F5 and feed the Como Zoo animal.
2. Confirm weightGain is 0.75 and happinessGain is 3.
3. Use F10 and confirm the animal's weight and happiness increase by those values.

What This Means

The methods are no longer limited to one hard-coded amount. The caller supplies the information, and the receiving method uses that information to update the correct object.