Unity ソフトウエアでゲーム制作#1モグラたたき編（24.Buttonでポーズ再開リトライ）

using System.Collections;
using System.Collections.Generic;
using UnityEngine;

public class UIController : MonoBehaviour
{
    //UIを開く
    public void OpenUI()
    {
        //表示をActiveに
        gameObject.SetActive(true);
    }

    //UI閉じる
    public void CloseUI()
    {
        //表示を非Activeに
        gameObject.SetActive(false);
    }
    //UIの初期化
    public virtual void InitUI()
    {
        //表示を非Activeに
        gameObject.SetActive(false);
    }

    private void Start()
    {
        //初期化
        InitUI();
    }
    
//    今回ハマった初期化
//    private void OnEnable()
//    {
//        InitUI();
//    }
}

public class PauseUIController : UIController
{
    public override void InitUI()
    {
        GameManager.Instance.PauseUIController=this;
        base.InitUI();
    }

}

public abstract class GameStateButton : MonoBehaviour
{
    public abstract void OnPress();
}

public class PauseButton : GameStateButton
{
    public override void OnPress()
    {
        GameManager.Instance.UpdateCurrentState(GameState.pause);
    }
}

public class ResumeButton : GameStateButton 
{
    public override void OnPress()
    {
        GameManager.Instance.UpdateCurrentState(GameState.resume);
    }
}

public class RetryButton: GameStateButton
{
    public override void OnPress()
    {
        GameManager.Instance.UpdateCurrentState(GameState.retry);
    }
}

public class QuitButton : GameStateButton
{
    public override void OnPress()
    {

    }
}

using UnityEngine.SceneManagement;

public class GameManager : Singleton<GameManager> 
{
    //省略
    public PauseUIController PauseUIController {  get; set; } 

    public void UpdateCurrentState(GameState newGameState)
    {
        CurrentGameState = newGameState;
        switch (newGameState)
        {
            //省略

            case GameState.pause:
                Time.timeScale = 0f;
                Pause();
                break;

            case GameState.resume:
                StartCoroutine(Resume());
                Time.timeScale = 0f;
            break;

            case GameState.retry:
                Retry();
                Time.timeScale = 1f;
                break;
                
          //省略

            default:
                throw new ArgumentOutOfRangeException
                    (nameof(newGameState),newGameState, $"UpdateCurrentStateにて予期せぬステート{newGameState}が指定されました");

        }

    }

    //省略

    private void Pause()
    {
        PauseUIController.OpenUI();
    }

    IEnumerator Resume()
    {
        PauseUIController.CloseUI();
        yield return new WaitForSecondsRealtime(0.8f);
        UpdateCurrentState(GameState.active);
    }

    private void Retry()
    {
        SceneManager.LoadScene(SceneManager.GetActiveScene().name);
        UpdateCurrentState(GameState.gamestart);
    }

    //省略

}