Package creation

Author: abrusle

LICENSE renamed to LICENSE.md

@@ -1,2 +1,43 @@
-# unity-scriptable-singletons
+# Scriptable Singletons
 Easy to use singleton implementation for ScriptableObjects in Unity.
+
+## Usage
+
+
+To make your ScriptableObject a singleton, place your asset instance in a _Resoures_ directory.
+
+Then, make your ScrptableObject class inherit from `ScriptableSingleton` and add the `AssetPathAttribute` with the path to your asset relative to the Resources folder.
+
+### Example
+
+Let's say that you need to access a scriptableObject called _MyGameSettings_ as a singleton.
+
+```c#
+public class MyGameSettings : ScriptableObject
+{
+    // ...
+}
+```
+
+Make sure only one asset for that object exists and place it in a valid Resources folder (e.g. `Assets/Resources/myGameSettingsAsset.asset`).
+
+
+Then, make a few changes to the class definition, as follows:
+```c#
+[AssetPath("myGameSettingsAsset")]
+public class MyGameSettings : ScriptableSingleton<MyGameSettings>
+{
+    // ...
+}
+```
+
+Note: if your asset is located in a subfolder within the Resources folder, the path specified in the AssetPath attribute should match with it. For example: an asset in `Assets/Resources/Foo/bar.asset` should have an attribute `[AssetPath("Foo/bar")]`.
+
+All set! You can access your asset instance with the `Instance` property.
+```c#
+MyGameSettings.Instance.DoSomething();
+```
+
+## Installation
+
+This package is compatible with the Unity Package Manager (UPM). Please refer to the official Unity documentation to [install this package from a git repository](https://docs.unity3d.com/2020.1/Documentation/Manual/upm-ui-giturl.html).

LICENSE.md.meta

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+{
+    "name": "Abrusle.ScriptableSingleton",
+    "references": [],
+    "includePlatforms": [],
+    "excludePlatforms": [],
+    "allowUnsafeCode": false,
+    "overrideReferences": false,
+    "precompiledReferences": [],
+    "autoReferenced": false,
+    "defineConstraints": [],
+    "versionDefines": [],
+    "noEngineReferences": false
+}

README.md

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+using System;
+
+[AttributeUsage(AttributeTargets.Class)]
+public sealed class AssetPathAttribute : Attribute
+{
+    public string Path { get; }
+
+    public AssetPathAttribute(string filePath)
+    {
+        Path = filePath;
+    }
+}

README.md.meta

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+using UnityEngine;
+
+public abstract class ScriptableSingleton<TObject> : ScriptableObject where TObject : ScriptableObject
+{
+    private static TObject _Instance;
+
+    public static TObject Instance
+    {
+        get
+        {
+            if (_Instance == null) CreateOrLoadInstance();
+            return _Instance;
+        }
+    }
+
+    private static void CreateOrLoadInstance()
+    {
+        string filePath = GetResourcePath();
+        if (!string.IsNullOrEmpty(filePath))
+            _Instance = Resources.Load<TObject>(filePath);
+        
+#if UNITY_EDITOR
+        if (_Instance != null) return;
+        _Instance = CreateInstance<TObject>();
+        UnityEditor.AssetDatabase.CreateAsset(_Instance, $"Assets/Resources/{filePath}.asset");
+#endif
+    }
+
+    private static string GetResourcePath()
+    {
+        var attributes = typeof(TObject).GetCustomAttributes(true);
+
+        foreach (object attribute in attributes)
+        {
+            if (attribute is AssetPathAttribute pathAttribute)
+                return pathAttribute.Path;
+        }
+        Debug.LogError($"{typeof(TObject)} does not have {nameof(AssetPathAttribute)}.");
+        return string.Empty;
+    }
+
+    protected virtual void Awake()
+    {
+#if UNITY_EDITOR
+        if (!Application.isPlaying)
+        {
+            if (_Instance != null && _Instance != this)
+            {
+                Debug.LogError($"An instance of {typeof(TObject)} already exist.");
+                DestroyImmediate(this);
+            }
+        }
+#endif
+    }
+}