Script Communication in Unity using GetComponent

In the example, there are three C# scripts coding three classes named Laser.cs, Enemy.cs, and Player.cs

We have a private variable in Player to value the number of remaining lives available to lose.

public class Player : MonoBehaviour
{
    [SerializeField]
    private int _lives = 4;
...

And the setter function accessible from outside the class (outside the .cs file)

public class Player : MonoBehaviour
{
    [SerializeField]
    private int _lives = 4;

    public void Damage()
    {
        _lives--;

        if (_lives < 1 )   // !_lives only works if _lives is type boolean
        {
            Destroy(this.gameObject);
        }
    }
...

From the Enemy.cs file we can access the public method in the Player class

Open the Enemy.cs file tab

When the Enemy gameObject collides with a Player gameObject, first damage the Player, then Destroy() the Enemy.

    private void OnTriggerEnter(Collider other)
    {
        // if other.name is Player
        // damage player
        // destroy this Enemy

        if (other.tag == "Player")
        {
            other.transform.GetComponent<Player>().Damage();
            Destroy(this.gameObject);
        }
    ...

For a moment, take a look at the <Player> csharp syntax. Consider the < > syntax outside of Unity.

Generic Methods — C# Programming Guide — C# | Microsoft Learn

The class contained in the < >’s would be a type in other programs. Here is the Microsoft Learn example:

public static void TestSwap()
{
    int a = 1;
    int b = 2;

    Swap<int>(ref a, ref b);
    System.Console.WriteLine(a + " " + b);
}

Instead of writing a different Swap function for int, float, and decimal types, simply specify which type (int, float, decimal) is desired and include inside the < >’s.

Here is the Swap declaration:

static void Swap<T>(ref T lhs, ref T rhs)
{
    T temp;
    temp = lhs;
    lhs = rhs;
    rhs = temp;
}

in the Swap function, there is no mention of int, float, or decimal.

so to use Swap with two int’s:

Swap<int>( a,b );

to Swap with two float’s: Swap<float>( f, g );

Swap<float>( f,g );

Return to Unity coding…

to call the Damage() method inside the Player class, use type Player:

The Player component in the Inspector view

            other.transform.GetComponent<Player>().Damage();

to return the “color” value inside the MeshRenderer class of Player, use type “MeshRenderer”:

Components of gameObject Player in Inpector view

other.transform.GetComponent<MeshRenderer>().Material.color;

Next is the best programming practice to check if the type (the class) exists.

    private void OnTriggerEnter(Collider other)
    {
        // if other.name is Player
        // damage player
        // destroy this Enemy

        if (other.tag == "Player")
        {
            Player player = other.transform.GetComponent<Player>();
            
            if( player != null )
            {
                player.Damage();
            }
            Destroy(this.gameObject);
        }
    ...