[Design Pattern] Prototype Pattern

One-line pattern summary

A pattern that creates new objects by cloning an existing prototype instead of calling a constructor.

Typical Unity use cases

• When creating runtime instances by cloning monster templates.
• When quickly duplicating objects whose creation cost is high.

Parts (roles)

• Prototype
• Clone
• Prototype Registry

Unity example (C#)

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

using UnityEngine;

[CreateAssetMenu(menuName = "Game/Enemy Archetype Data")]
public sealed class EnemyArchetypeData : ScriptableObject
{
    public int baseHealth;
    public float moveSpeed;

    public EnemyRuntimeData CloneRuntimeData()
    {
        return new EnemyRuntimeData(baseHealth, moveSpeed);
    }
}

public sealed class EnemyRuntimeData
{
    public int CurrentHealth;
    public float CurrentMoveSpeed;

    public EnemyRuntimeData(int currentHealth, float currentMoveSpeed)
    {
        CurrentHealth = currentHealth;
        CurrentMoveSpeed = currentMoveSpeed;
    }
}

Advantages

• Object creation responsibilities are well organized, which makes dependency management easier.
• Creation policies can be changed flexibly by environment or situation.

Things to watch out for

• Avoid introducing overly abstract creation layers for simple problems.
• As creation rules increase, keeping documentation and tests in sync becomes more important.

Interaction diagram

This shows the flow where a registered prototype is cloned and then customized with runtime values.

flowchart LR

  spawner["Spawner"]
  registry["Prototype Registry"]
  prototype["Enemy Prototype"]
  clone["Clone()"]
  customize["Set Runtime Values"]
  result["Spawned Enemy"]

  spawner -->|request type| registry
  registry --> prototype
  prototype --> clone
  clone --> customize
  customize --> result