unity-pattern-mvp

name	unity-pattern-mvp
description	MVP
category	unity
source	unity-design-patterns-skills
source_path	patterns/mvp/SKILL.md

MVP

Purpose

Keep UI presentation logic out of the view by routing it through a presenter that talks to a passive view contract.

Use When

• A panel or HUD is accumulating too much logic.
• You want to test UI behavior without a live scene.
• View rendering and interaction rules should be separated.

Avoid When

• The widget is tiny and short-lived.
• The view would still keep all domain logic.

Unity Implementation Recipe

1. Define a passive view interface.
2. Move interaction logic into a presenter.
3. Keep model or service dependencies out of the view.
4. Manage subscriptions with scene lifetime.

Common Pitfalls

• A presenter that becomes a pass-through because the view still owns the logic.
• Presenter code coupled directly to too many Unity APIs.

Minimal Unity Sketch

public interface IHealthView
{
    void SetValue(float normalized);
}

public sealed class HealthPresenter
{
    private readonly IHealthView _view;
    public HealthPresenter(IHealthView view) => _view = view;
    public void OnHealthChanged(int current, int max) => _view.SetValue((float)current / max);
}

Response Shape

• Say whether MVP is actually the right fit.
• Map it to concrete Unity types, ownership, and lifecycle.
• Prefer a production-shaped skeleton over a long tutorial dump.
• Call out the simpler alternative if this pattern would be overengineering.