🧩 Functions in Unity

Functions (or methods) in Unity are a way to organize your code into separate blocks to make it clearer, more convenient, and more reliable. If you want the same set of actions to run in different places — you can move them into a separate function and simply call it when needed.

Instead of writing the same lines over and over, you create a function once and then call it by name. This saves time, makes the code cleaner, and helps you find bugs more easily.

Functions can perform actions (for example, make the player jump, heal the player, or play a sound) or return values (for example, calculate points or check if the enemy is alive). You can also pass parameters to them — for example, "add 5 to health" or "spawn 3 enemies".

In Unity, you can use both built-in functions (for example, Start() and Update()) and write your own. That's exactly what we’ll learn to do now — step-by-step and easy to follow.

✨ How to create your own function

A function in Unity is a block of code that performs a specific action. To create one, you need to write it inside a class but outside other functions. Usually, we place them near Start() or Update() in the script body.

Every function consists of four parts: the return type (for example, void), the name, parentheses for parameters (even if there are none), and curly braces containing the code.

For example, you can create a Jump() function to make the character jump. Or a HealPlayer(int amount) function to add health. It all depends on the task — the key thing is that you control what happens inside the function and when it’s called.

✅ Void function (returns nothing)

If a function just performs an action and does not return any value, it’s marked with the word void. Such functions are useful when you simply need to do something — for example, display a message or play a sound.


using UnityEngine;

public class CSharpScript : MonoBehaviour
{
    // Start is called once when the object starts
    void Start()
    {
        SayHello();
    }

    // Update is called every frame
    void Update()
    {
        
    }

    void SayHello()
    {
        Debug.Log("Hello, Unity!");
    }
}

Here we created a SayHello() function that prints text to the console. We call it from Start() so it runs at the start. Functions like these are the basis for organizing code — they keep it neat and readable.

⚖️ Function with a parameter

Functions can take parameters — extra data you pass when calling them. This makes the function more flexible: it can behave differently depending on the input values.


using UnityEngine;

public class CSharpScript : MonoBehaviour
{
    // Start is called once when the object starts
    void Start()
    {
        HealPlayer(10);
    }

    // Update is called every frame
    void Update()
    {
        
    }

    void HealPlayer(int amount)
    {
        Debug.Log("Healing the player by " + amount + " health points");
    }
}

We created a HealPlayer function that takes one parameter — amount. When calling HealPlayer(10), the console shows a healing message for 10 points. You can call the same function with other numbers — and the behavior will change.

🔄 How to call your function

To call a function, just write its name and parentheses. If it has parameters, pass the required values inside. You can call it from Start(), Update(), or another function.

In the previous examples, we already called functions — SayHello() and HealPlayer(10). That’s what a function call is. Without it, the function won’t run — it will just exist in the code.

🔢 Function that returns a value

Sometimes you need a function to calculate something and return the result. To do this, instead of void you specify the return type — for example, int or bool. Such a function can be used as part of another expression.


using UnityEngine;

public class CSharpScript : MonoBehaviour
{
    // Start is called once when the object starts
    void Start()
    {
        int score = GetScore();
        Debug.Log("Current score: " + score);
    }

    // Update is called every frame
    void Update()
    {
        
    }

    int GetScore()
    {
        return 42;
    }
}

Here the GetScore() function returns a number. We store it in a variable and print it to the console. Such functions are especially useful when you need a result — for example, an object’s position, the player’s health, or a true/false flag.