FactoryMethod

Factory Method

One-line pattern summary

A pattern that delegates the actual creation responsibility of a factory method to subclasses.

Typical Unity use cases

• When projectile creation rules differ by weapon type.
• When type-specific initialization logic should be separated.

Parts (roles)

• Creator
• Concrete Creator
• Product

Unity example (C#)

The code below is a simplified Unity example based on the scenario described above.

using UnityEngine;

public interface IProjectile
{
    void Fire(Vector3 startPosition, Vector3 direction);
}

public abstract class ProjectileSpawner : MonoBehaviour
{
    public void Shoot(Vector3 startPosition, Vector3 direction)
    {
        IProjectile projectile = CreateProjectile();
        projectile.Fire(startPosition, direction);
    }

    protected abstract IProjectile CreateProjectile();
}

Advantages

• It clarifies module boundaries and reduces coupling.
• Features can be extended or integrated without modifying existing code.

Things to watch out for

• If wrapper layers become too deep, debugging gets harder.
• Interfaces should stay small so responsibility boundaries do not blur.

Interaction diagram

This shows the flow where the parent keeps the creation procedure while subclasses choose the actual type.