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The best way to implement singleton pattern in Unity.

Home Page: https://en.wikipedia.org/wiki/Singleton_pattern

License: MIT License

C# 100.00%

singleton singleton-pattern singleton-standard singletonpattern design-patterns design-pattern csharp csharp-code csharp-library csharp-script

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unitysingleton's Issues

Awake DestroyObject with condition?

  protected virtual void Awake()
    {
        if (instance == null)
        {
            instance = this as T;
            DontDestroyOnLoad(gameObject);
        }
        else if (instance != this)
        {
            //If there is already an instance of this class, destroy the object we just created.
            Debug.LogWarning("Attempted to spawn more then one singleton object. destroying new instance of " + gameObject.ToString() + "\nIf you would like more than one instance, ensure that the class you have written does not Inherit from a Singleton class.");
            Destroy(gameObject);
        }
    }

I found another snippet from Naphier which the instance!=this make sense when destroy it.

Could you please explain it why you didn't add condition? Thanks.

Add UPM support

Add Unity Package Manager setup instructions and include package.json file.

How about "public abstract class MonoSingleton<T> : MonoBehaviour where T : MonoSingleton<T>"

Would it be better to add a singleton class which is not extended from Monobehaviour?

Maybe it's better to have a singleton class which is not extended from Monobehaviour. And it can be used to add some class to manager global data or implement data.

In some cases we should use this pattern, it differs from the traditional "Global singleton pattern", the purpose of "Scene Singleton Pattern" is to ensure that there is only one instance of the class in a given scene, but it does not require that instance to persist across scenes. This pattern is useful when you need to manage certain assets or features in a single scene, but you don't want those assets or features to remain present when the scene is switched.

Great job, could even be extended to support editor mode

Thanks for the code, I believe it could be further enhanced to support editor mode, like the following:

using System.Diagnostics.CodeAnalysis;
using JetBrains.Annotations;
using UnityEngine;

namespace Z
{
    [PublicAPI]
    [ExecuteAlways]
    public abstract class Singleton<T> : MonoBehaviour where T : Component
    {
        private static T _instance;

        public static T Instance
        {
            get
            {
                if (_instance != null)
                    return _instance;

                _instance = FindObjectOfType<T>();

                if (_instance != null)
                    return _instance;

                var o = new GameObject($"{typeof(T).Name} (Singleton)");

                _instance = o.AddComponent<T>();

                return _instance;
            }
        }

        [SuppressMessage("ReSharper", "VirtualMemberNeverOverridden.Global")]
        protected virtual void Awake()
        {
            if (_instance == null)
            {
                _instance = this as T;

                if (Application.isPlaying)
                {
                    DontDestroyOnLoad(gameObject);
                }
            }
            else
            {
                if (Application.isPlaying)
                {
                    Destroy(gameObject);
                }
                else
                {
                    DestroyImmediate(gameObject);
                }
            }
        }
    }
}

Not PR-ing, just a suggestion :)

Wouldn't it be nice to "seal" the Awake function?

protected virtual void Awake() {
    if (_instance == null) {
        _instance = this as T;
        DontDestroyOnLoad(gameObject);
    }
    else {
        Destroy(gameObject);
    }
}

The Awake() function is the key part to make the derived singleton class persistent across scenes and prevent duplicates, but it is marked as protected virtual, so that one could accidentally override it but forgot to add the base.Awake() call, which would then break things apart, and it's hard to debug...

I think maybe we can improve by doing sth like this?

private void Awake() {
    if (_instance == null) {
        _instance = this as T;
        DontDestroyOnLoad(gameObject);
        Initialize();
    }
    else {
        Destroy(gameObject);
    }
}

protected virtual void Initialize() { }

unitycommunity / unitysingleton Goto Github PK

unitysingleton's People

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unitysingleton's Issues

Awake DestroyObject with condition?

Add UPM support

How about "public abstract class MonoSingleton<T> : MonoBehaviour where T : MonoSingleton<T>"

Would it be better to add a singleton class which is not extended from Monobehaviour?

Scene Singleton Pattern

Great job, could even be extended to support editor mode

Wouldn't it be nice to "seal" the Awake function?

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