chandler-11 The Singleton Pattern Must Be a Class

Closes #11.

composer.lock

@@ -4,7 +4,7 @@
         "Read more about it at https://getcomposer.org/doc/01-basic-usage.md#installing-dependencies",
         "This file is @generated automatically"
     ],
-    "content-hash": "0aa468953e3be7c5754eadbc5f3c6234",
+    "content-hash": "ec942d4b143e30d41b04837c5d8c09cf",
     "packages": [
         {
             "name": "doctrine/lexer",
@@ -2130,16 +2130,16 @@
         },
         {
             "name": "symfony/translation",
-            "version": "v5.4.1",
+            "version": "v5.4.2",
             "source": {
                 "type": "git",
                 "url": "https://github.com/symfony/translation.git",
-                "reference": "8c82cd35ed861236138d5ae1c78c0c7ebcd62107"
+                "reference": "ff8bb2107b6a549dc3c5dd9c498dcc82c9c098ca"
             },
             "dist": {
                 "type": "zip",
-                "url": "https://api.github.com/repos/symfony/translation/zipball/8c82cd35ed861236138d5ae1c78c0c7ebcd62107",
-                "reference": "8c82cd35ed861236138d5ae1c78c0c7ebcd62107",
+                "url": "https://api.github.com/repos/symfony/translation/zipball/ff8bb2107b6a549dc3c5dd9c498dcc82c9c098ca",
+                "reference": "ff8bb2107b6a549dc3c5dd9c498dcc82c9c098ca",
                 "shasum": ""
             },
             "require": {
@@ -2207,7 +2207,7 @@
             "description": "Provides tools to internationalize your application",
             "homepage": "https://symfony.com",
             "support": {
-                "source": "https://github.com/symfony/translation/tree/v5.4.1"
+                "source": "https://github.com/symfony/translation/tree/v5.4.2"
             },
             "funding": [
                 {
@@ -2223,7 +2223,7 @@
                     "type": "tidelift"
                 }
             ],
-            "time": "2021-12-05T20:33:52+00:00"
+            "time": "2021-12-25T19:45:36+00:00"
         },
         {
             "name": "symfony/translation-contracts",
@@ -2305,16 +2305,16 @@
         },
         {
             "name": "symfony/yaml",
-            "version": "v5.4.0",
+            "version": "v5.4.2",
             "source": {
                 "type": "git",
                 "url": "https://github.com/symfony/yaml.git",
-                "reference": "034ccc0994f1ae3f7499fa5b1f2e75d5e7a94efc"
+                "reference": "b9eb163846a61bb32dfc147f7859e274fab38b58"
             },
             "dist": {
                 "type": "zip",
-                "url": "https://api.github.com/repos/symfony/yaml/zipball/034ccc0994f1ae3f7499fa5b1f2e75d5e7a94efc",
-                "reference": "034ccc0994f1ae3f7499fa5b1f2e75d5e7a94efc",
+                "url": "https://api.github.com/repos/symfony/yaml/zipball/b9eb163846a61bb32dfc147f7859e274fab38b58",
+                "reference": "b9eb163846a61bb32dfc147f7859e274fab38b58",
                 "shasum": ""
             },
             "require": {
@@ -2360,7 +2360,7 @@
             "description": "Loads and dumps YAML files",
             "homepage": "https://symfony.com",
             "support": {
-                "source": "https://github.com/symfony/yaml/tree/v5.4.0"
+                "source": "https://github.com/symfony/yaml/tree/v5.4.2"
             },
             "funding": [
                 {
@@ -2376,7 +2376,7 @@
                     "type": "tidelift"
                 }
             ],
-            "time": "2021-11-28T15:25:38+00:00"
+            "time": "2021-12-16T21:58:21+00:00"
         },
         {
             "name": "tracy/tracy",
@@ -4510,7 +4510,8 @@
     "prefer-stable": false,
     "prefer-lowest": false,
     "platform": {
-        "php": "^7.3"
+        "ext-yaml": "*",
+        "php": "^7.4"
     },
     "platform-dev": [],
     "plugin-api-version": "2.2.0"

src/Classes/Singleton.php

@@ -0,0 +1,42 @@
+<?php
+
+declare(strict_types = 1);
+
+namespace Chandler\Classes;
+
+use Chandler\Interfaces\Singleton as SingletonInterface;
+
+/**
+ * @package Chandler\Classes
+ */
+abstract class Singleton implements SingletonInterface
+{
+    /**
+     * @var array
+     */
+    private static array $instances = [];
+
+    /**
+     * TODO: Add a description.
+     *
+     * @return void
+     */
+    final private function __clone() {}
+
+    /**
+     * TODO: Add a description.
+     */
+    abstract protected function __construct();
+
+    /**
+     * @return static
+     */
+    public static function getInstance(): self
+    {
+        if (array_key_exists(static::class, self::$instances)) {
+            return self::$instances[static::class];
+        } else {
+            return self::$instances[static::class] = new static();
+        }
+    }
+}

src/Interfaces/Singleton.php

@@ -0,0 +1,16 @@
+<?php
+
+declare(strict_types = 1);
+
+namespace Chandler\Interfaces;
+
+/**
+ * @package Chandler\Interfaces
+ */
+interface Singleton
+{
+    /**
+     * @return static
+     */
+    public static function getInstance(): self;
+}