Conditional statements control the execution of your Unity game's code, a programming concept known as control flow.

One of the simplest use cases for conditional statements is moving the character in a game you're building in the Unity Game Engine.

If the player presses the W key, the character should move forward. If they press the S key, the character should move backward. You can use a conditional statement to accomplish this.

This article assumes you're familiar with Booleans, the backbone of conditional statements, as well as variables, operators, and numbers.

If you're a visual learner, scroll to the bottom for the video version, or you can watch it on YouTube.

Conditional Statements in C# Explained

You'll eventually encounter scenarios where you want to act only when a specific condition is satisfied.

For example, you might want to increase the player's health if they interact with a health orb, or turn the 3D model into a ragdoll when the player's health reaches 0.

The condition for the player's health to increase is the interaction with a health orb. Similarly, the condition for the character's 3D model to become a ragdoll is the player's health reaching 0.

You only proceed to the next step when these conditions are satisfied, either increasing the player's health or turning the 3D model into a ragdoll.

By placing conditions in certain parts of your game's code, you're controlling the flow of execution based on those conditions.

This control ensures your game behaves how you want it to when you want it to.

The two conditional statements you'll use the most when making a game in Unity are the if and switch statements. Let's explore the if statement first.

if Statements

An if statement in C# is written similarly to how you do so in plain English.

If the player picks up some money, the money in their inventory increases. Here's how you would accomplish the same thing with an if statement.

/*
  * Classes are discussed in more detail in a separate article,
  * but just go with this for now.
*/
// This creates a player instance.
var player = new Player();

if (player.HasPickedUpMoney() == true)
  player.MoneyHeld += 250;

The code in the parentheses represents the condition, and conditions must be a Boolean value.

A Boolean value can only be either true or false. Think of an if statement as saying, "If the condition is true, execute the code inside the code block. If not, skip the code in the code block, and execute whatever comes after the if statement."

You can also use multiple conditions in an if statement.

One of the earlier examples discussed increasing the player's health whenever they interacted with a health orb.

var player = new Player();

var healthOrb = 15;

// if (player.HasPickedHealthOrb(healthOrb) == true)
//   player.Health += healthOrb;

/*
  * 'HasPickedHealthOrb' returns a Boolean value,
  * so the code above can be shortened, like so.
*/
if (player.HasPickedHealthOrb(healthOrb))
  player.Health += healthOrb;

This code partially works but has a problem. If the player continuously interacts with health orbs at full health, their health will keep increasing infinitely.

That's a bug, and it's caused by increasing the player's health without first checking if it's already at its maximum.

You can add a second condition to ensure the player's health increases if they interact with a health orb and they're health is below the maximum.

The symbol representing the word "and" in the conditions is a double ampersand "&&". It's one of the logical operators.

var player = new Player();

const int MaxHealth = 100;

var healthOrb = 15;

/*
  * Curly braces {} are optional when the 'if' statement only has one line,
  * but are mandatory for multiple.
*/
if (player.HasPickedHealthOrb(healthOrb) && player.Health < MaxHealth)
{
  player.Health += healthOrb;
}

To help you understand better, you can read the above code as, "If the player interacts with a health orb and their health is below the maximum, add them 15 hit points (HP)."

Consider another scenario. Let's say the game you're making in Unity has fall damage in addition to taking damage from enemy attacks.

In this case, the player's health reduces when one of two conditions is satisfied:

• The player jumped down from a high platform and landed hard, or...
• An enemy attacked the player.

You can implement this using another logical operator, commonly referred to as the OR operator. Its symbol is a double pipe "||".

var player = new Player();

var fallDamageHeight = 20;

if (player.HasFallenFrom(fallDamageHeight) || player.IsAttacked())
{
  player.Health -= 10;
}

You can read the code above as, "If the player falls from a high point or an enemy attacks them, take away 10 hit points."

Nested if Statements

It's possible to place if statements inside the code block of other if statements. This approach is called nesting. Nesting can occur if a series of conditions must be satisfied.

Let's say you want to deduct 10 HP only when the player's health is above 10 HP after they're attacked or fall hard. Here's how you'd accomplish it.

var player = new Player();

var fallDamageHeight = 20;

// First condition to satisfy.
if (player.HasFallenFrom(fallDamageHeight) || player.IsAttacked())
{
  /*
    * This is a nested 'if' statement.
    * It only executes when one of the conditions above is satisfied.
  */
  if (player.Health > 10)
    player.Health -= 10;
}

The code now first checks if the player has fallen from a high platform or if an enemy has attacked them.

Once this condition is satisfied, you now know the player's health should reduce, so you check a second time to see how much remaining health they have to determine how much HP you'll deduct.

else and else if Statements

Suppose you're building a fighting game in Unity where each fighter has a special meter that lets them perform special moves as the meter fills.

The meter enables a unique special move at 25%, 50%, 75%, and the ultimate move at 100%; however, only one can be performed before the meter resets.

Each percentage mark represents a scenario to check for. You can combine an if statement with an else if and else statements to achieve this.

var player = new Player();

if (player.SpecialMeter == 25)
  Debug.Log("Sonic Pulse available.");

else if (player.SpecialMeter == 50)
  Debug.Log("Flame Fist available.");

else if (player.SpecialMeter == 75)
  Debug.Log("Gatling Gun available.");

else
  Debug.Log("Ultimate ready. Let's rock!");

The code searches the conditions in each if and else if statement from top to bottom and stops when it finds the first true condition, executing only that code block.

An else statement doesn't have a condition and must come after the if and else if statements.

The code in an else block only executes if the conditions in the if and else if statements are all false.

You can also use an if and an else statement without else if in between for scenarios where it's one thing or the other.

For example, the main character in your Unity game could play a voice line if the player tries to fire their gun with no ammo.

The code would read, "If the player has ammo, fire the gun. Otherwise, play the 'I need ammo!' voice audio clip."

var player = new Player();

var noAmmoVoiceLine = "I need ammo!";

if (player.AmmoCount > 0)
  player.FireGun();

else
  player.PlayAudioClip(noAmmoVoiceLine);

Remember that else if and else statements can only be used immediately after an if statement - they can't exist on their own.

On the contrary, if statements can exist alone without supporting else if or else statements.

switch Statements

switch statements are generally similar to if statements. The biggest difference is how they're declared.

You create them using the switch keyword, and, instead of the parentheses containing a check, a value is placed in there to be tested for different scenarios. The value doesn't have to be a Boolean.

Here's how you implement the earlier example discussing special moves in a fighting game using a switch statement.

var player = new Player();

switch (player.SpecialMeter)
{
  case 25:
    Debug.Log("Sonic Pulse available.");
    break;

  case 50:
    Debug.Log("Flame Fist available.");
    break;

  case 75:
    Debug.Log("Gatling Gun available.");
    break;

  default:
    Debug.Log("Ultimate ready. Let's rock!");
    break;
}

The meter's percentage is in parentheses, and each case inside the switch statement checks for a specific scenario.

You can read it as, "In the case the meter is at 25%, unlock the Sonic Pulse special move. In the case the meter is at 50%, unlock the Flame Fist special move."

The break keyword is used after each case to ensure the code only executes the true case. Removing this would execute the code for the other cases below the true one.

Similar to if statements, a default case is included at the bottom when none of the cases above it are true; the switch statement equivalent of the else block in if statements.

switch Expressions

A switch expression is similar to a switch statement but is declared differently.

Unlike the switch statement, which is a code block, a switch expression returns a value you can store in a variable.

var player = new Player();

// Switch expression.
var specialMove = player.SpecialMeter switch
{
  25 => "Sonic Pulse available.",
  50 => "Flame Fist available.",
  75 => "Gatling Gun available",
  _ => "Ultimate ready. Let's rock!"
};

Debug.Log(specialMove);

The main differences between a switch expression and a switch statement are:

• The tested value in a switch expression comes before the switch keyword, but after it in switch statements.
• Switch expressions return a value. switch statements do not.
• Switch expressions use an equal sign and an arrow for each scenario, while switch statements use the case keyword.
• Switch expressions use an underscore when all the scenarios are false, while a switch statement uses the default keyword.

if Statement vs. switch Statement: Which Should You Use?

Both statements accomplish the same goal, and choosing one over the other often comes down to personal preferences.

Given that switch statements must include the case keyword at the beginning and the break keyword at the end, they may be more verbose to write than an if statement.

You might find it easier working with if statements if there are multiple things you want to do inside each code block for each scenario.

switch statements may be easier to read and work with when you only have a line or two you want to execute for each scenario.

Recap

• Conditional statements control the flow of code execution.
• The two most common statements are if and switch statements.
• The condition in an if or else if statement must be a Boolean.
• The value under test in a switch statement can be multiple types, such as a number, string, or Boolean.
• Switch expressions also use the switch keyword and return a value.

This article is the eighth in a series breaking down common C# concepts used in game development with the Unity Game Engine.

The next one discusses how to use loops when working with multiple related items.

Here's the complete list of articles in the series:

• A Game Developer's Guide to Variables in C#
• A Game Developer's Guide to Constants in C#
• A Game Developer's Guide to Numbers in C#
• A Game Developer's Guide to Operators in C#
• A Game Developer's Guide to Strings in C#
• A Game Developer's Guide to Booleans in C#
• A Game Developer's Guide to Enums in C#
• A Game Developer's Guide to Conditional Statements in C# (you are here)
• A Game Developer's Guide to Loops in C#
• A Game Developer's Guide to Classes in C#
• A Game Developer's Guide to Access Modifiers in C#
• A Game Developer's Guide to Fields & Properties in C#
• A Game Developer's Guide to Methods in C#
• A Game Developer's Guide to Lists & Arrays in C#
• A Game Developer's Guide to Dates & Times in C#