Variables

A variable can be compared to a container that includes a value that may change over time. When using variables, we usually need to: (1) declare the variable by specifying its type, (2) assign a value to this variable, and (3) possibly combine this variable with other variables using operators, as illustrated in the next code snippet.

int myAge;//we declare the variable myAge

myAge = 20;// we set the variable myAge to 20

myAge = myAge + 1; //we add 1 to the variable myAge

In the previous example, we have declared a variable called myAge and its type is int (as in integer). We save the value 20 in this variable, and we then add 1 to it.

Note that, contrary to UnityScript, where the keyword var is used to declare a variable, in C# the variable is declared using its type followed by its name. As we will see later, we will also need to use what is called an access modifier in order to specify how and from where this variable can be accessed.

Also note that in the previous code, we have assigned the value myAge + 1 to the variable myAge; the = operator is an assignment operator; in other words, it is there to assign a value to a variable and is not to be understood in a strict algebraic sense (i.e., that the values or variables on both sides of the = sign are equal).

To make C# coding easier and leaner, you can declare several variables of the same type in one statement. For example, in the next code snippet, we declare three variables v1, v2, and v3 in one statement. This is because they are of the same type (i.e., they are integers).

int v1,v2,v3;

int v4=4, v5=5, v6=6;

In the code above, the first line declares the variables v1, v2, and v3. All three variables are integers. In the second line of code, not only do we declare three variables simultaneously, but we also initialize them by setting a value for each of these variables.

When using variables, there are a few things that we need to determine including their name, their type and their scope:

  • Name of a variable: a variable is usually given a unique name so that it can be identified easily and uniquely. The name of a variable is usually referred to as an identifier. When defining an identifier, it can contain letters, digits, a minus, an underscore or a dollar sign, and it usually begins with a letter. Identifiers cannot be keywords, such as the keyword if, for example.
  • Type of variable: variables can hold several types of data, including numbers (e.g., integers, doubles or floats), text (e.g., strings or characters), Boolean values (e.g., true or false), arrays, objects (we will see the concept of arrays later in this chapter) or GameObjects (i.e., any object included in your scene), as illustrated in the next code snippet.
  • Variable declaration: variables need to be declared so that the system knows what you are referring to if you use this variable in your code. The first step in using a variable is to declare or define this variable. At the declaration stage, the variable does not have to be assigned a value, as this can be done later. In the next example, we declare a variable called myName and then assign the value “My Name” to it.
  • Scope of a variable: a variable can be accessed in specific contexts that depend on where in the script the variable was initially declared. We will look at this concept later.
  • Accessibility level: as we will see later, a C# program consists of classes; for each of these classes, the methods and variables within can be accessed depending on their accessibility levels and we will look at this principle later.
  • String: same as text.
  • Int: integer (1, 2, 3, etc.).
  • Boolean: true or false.
  • Float: with a fractional value (e.g., 1.2f, 3.4f, etc.).
  • Arrays: a group of variables of the same type. If this is unclear, not to worry, this concept will be explained further in this chapter.

string myName = “Patrick”;//the text is declared using double quotes

int currentYear = 2017;//the year needs no decimals and is declared as an integer

float width = 100.45f;//the width is declared as a float (i.e., with decimals)

string myName;

myName = “My Name”

Common variable types include:

  • String: same as text.
  • Int: integer (1, 2, 3, etc.).
  • Boolean: true or false.
  • Float: with a fractional value (e.g., 1.2f, 3.4f, etc.).
  • Arrays: a group of variables of the same type. If this is unclear, not to worry, this concept will be explained further in this chapter.
  • GameObject: a game object (any game object in your scene).

You can drag and drop this file to an empty object, play the scene and see the result in the Console window. You can also, if you wish, modify the file using Mono develop or any script editor of your choice.

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Variables.cs