Applying Single Responsibility Principle to MonoBehaviours

You will refactor monolithic controller scripts into specialized classes to ensure each component performs exactly one distinct game function.

In this lesson, you will learn how to refactor bloated "God Scripts" into clean, specialized components to make your codebase modular and maintainable.

The Problem with "God Scripts"

In Unity, it’s common for beginners to put everything—movement, health, input, and UI updates—inside a single PlayerController.cs. As your project grows, this class becomes a "God Script": it knows too much, does too much, and breaks whenever you change even the smallest feature.

The Single Responsibility Principle (SRP) states that a class should have only one reason to change. If your PlayerController needs to be modified because you updated the UI and because you tweaked the movement physics, it has too many responsibilities.

Refactoring for Clarity

To apply SRP, you break that monolithic script into smaller, focused classes. Instead of one script doing everything, you compose your GameObject using multiple, specialized components that work together.

For example, take a look at this refactored approach:

InputHandler.cs: Only captures player input.
Mover.cs: Only handles physics and transform updates.
Health.cs: Only tracks damage and death state.

Instead of the Mover asking the InputHandler what the keys are, the InputHandler passes the movement direction to the Mover via a public method.

public class Mover : MonoBehaviour 
{
    // This script only cares about how to move based on provided data
    public void Move(Vector3 direction) 
    {
        transform.Translate(direction * Time.deltaTime);
    }
}

By decoupling these, your Mover doesn’t care if input comes from a keyboard, a controller, or an AI script. If you decide to change the movement physics, you don't risk breaking your health tracking logic. This makes debugging significantly faster because you know exactly which script is responsible for a specific behavior. When you add new features, you simply attach new components rather than writing "spaghetti code" inside an existing, massive script.

Key Takeaway: A class should perform exactly one distinct function; by splitting your logic into specialized MonoBehaviours, you create a flexible architecture where components can be easily tested, swapped, or reused.