Lesson 04.1 – Creating the Player class and its properties

Lesson Objectives

At the end of this lesson, you will know…

• How to determine the properties for a class.
• How to select the correct “datatype” for each property.
• How to create a class.
• Two different ways to store property values.

What are properties?

The properties of a class, or object, are the pieces of information about it that can be different in each object, or could change while the program is running.

In an RPG, that would be things such as the amount of gold, experience points, items in inventory, etc. We need a place to hold those values for the object, and the ability to change those values.

What are datatypes?

The datatype is just a geeky way to answer the question, “What kind of information are we going to store in this property, or variable?”

To start out, we’re only going to look at two datatypes: integers and string.

An integer, if you remember back to math class, is a whole number – one that doesn’t have any decimal value. This is what we need for the player’s experience points, gold, and level.

A string is letters, miscellaneous characters (such as, @#$%^&*), or numbers treated as letters.

We don’t need any strings for our Player class, but we will have them in other classes. If you want to save a number to a string property or variable, it needs to be in quotes (“1”, instead of 1), or you need to convert it from a number to a string (we’ll see that a little later).

Once you declare the datatype for a property or variable, you can only store that type of data in it. So, you can’t say that ExperiencePoints has an integer datatype, then try to save a string in it.

Note: Adding together strings that contain numbers in them acts differently from adding together numeric datatypes.

For example, if you try to add together the integers 1 and 2, you’ll get an answer of 3. But when you add the strings “1” and “2”, you get “12”. This is called “concatenating strings”.

The properties of the Player class

Our Player class is going to be very simple. The only things we care about it (for now) are:

• The player’s current hit points (in case they’ve lost any during battle)
• The player’s maximum hit points (when they are fully healed)
• The amount of gold the player has
• The amount of experience points the player has
• The player’s current level
• The datatype for all these properties will be “integer”, since we only need to store whole numbers in them.

In a future lesson, we’ll add their items in inventory and the quests they have.

Creating the Player class

Link to video on YouTube

Step 1: Start Visual Studio Express 2013 for Desktop, and open the solution.

Step 2: In the solution explorer, right-click on the “Engine” project. Select “Add”, then “Class”. Change the name of the class from “Class1.cs” to “Player.cs” (be sure to keep the original “.cs” at the end, but don’t add a second “.cs”). Press the “Add” button.

Now you are editing the code for the Player class.

Step 3: Change line 9 so it says “public class Player”. We’ll discuss why in a minute.

Step 4: Go to the end of line 10 (to the right of the “{” character) and press the enter key, to make some space to add the properties.

Step 5: Type in these lines:

public int CurrentHitPoints { get; set; }
public int MaximumHitPoints { get; set; }
public int Gold { get; set; }
public int ExperiencePoints { get; set; }
public int Level { get; set; }

Notice that we don’t have a space between the words “current”, “hit”, and “points” (along with the MaximumHitPoints and ExperiencePoints). You can’t have a space in the middle of a property, or variable name. So, we use upper-case letters to show where each word starts. This isn’t a requirement of C#, but it is how many programmers write property names. It’s known as the “Pascal case” style.

NOTE: In C#, matching upper and lower case is important. A variable, or property, named “test” is different from one named “Test”.

What did you just do?

OK, you’ve typed in the code, but what does all of it mean?

First, we’ll start with “public”. This is known as the “scope”. It signifies what other parts of the solution can see the class or property. “Public” means that it is visible throughout the whole solution. This way, the UI project will be able to create a Player object and read the values of its properties.

We’ll talk about some of the other scope options in later lessons.

Next, what’s happening on lines 11 through 15?

These are the properties of the Player class. They’re public, since we need to have them visible everywhere. The “int” says that their datatype is an integer. Then we have the name of the property. Finally, there is a “{ get; set; }” after each property. Those signifies that we have a property where we can “get” a value (read what is stored in the property) and “set” a value (store a value in the property). We’ll see these in action soon.

What’s on lines 1 through 5?

That is a bunch of stuff we don’t need for this class. But, when you create a new class in Visual Studio, it adds that in automatically, in case you will need it. For now, don’t worry about it.

Summary

Now you’ve created the Player class. Once your program creates (instantiates) a Player object, it will be able to read and change the values of the object’s properties.

Source code for this lesson

Source code on GitHub

Source code on DropBox

Next Lesson: Lesson 05.1 – Creating objects from classes

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