Introduce singleton to prepare for Block Editor class

eth-embed-anchor-fm.php

@@ -45,5 +45,7 @@ add_action( 'plugins_loaded', __NAMESPACE__ . '\action_plugins_loaded' );
 /**
  * Load plugin classes.
  */
+require_once __DIR__ . '/inc/trait-singleton.php';
 require_once __DIR__ . '/inc/class-plugin.php';
+
 Plugin::get_instance();

inc/class-plugin.php

@@ -11,6 +11,8 @@ namespace ETH_Embed_Anchor_FM;
  * Class Plugin.
  */
 class Plugin {
+	use Singleton;
+
 	/**
 	 * Regex pattern to match URL to be oEmbedded.
 	 *
@@ -39,34 +41,6 @@ class Plugin {
 	 */
 	private const SHORTCODE_TAG = 'eth_anchor_fm';
 
-	/**
-	 * Singleton.
-	 *
-	 * @var Plugin
-	 */
-	private static $_instance = null;
-
-	/**
-	 * Implement singleton.
-	 *
-	 * @return Plugin
-	 */
-	public static function get_instance(): Plugin {
-		if ( ! is_a( self::$_instance, __CLASS__ ) ) {
-			self::$_instance = new self();
-			self::$_instance->_setup();
-		}
-
-		return self::$_instance;
-	}
-
-	/**
-	 * Silence is golden!
-	 */
-	private function __construct() {
-		// Add nothing here.
-	}
-
 	/**
 	 * Register hooks.
 	 *

inc/trait-singleton.php

+<?php
+/**
+ * Singleton trait.
+ *
+ * @package ETH_Embed_Anchor_FM
+ */
+
+namespace ETH_Embed_Anchor_FM;
+
+/**
+ * Trait Singleton.
+ */
+trait Singleton {
+	/**
+	 * Singleton.
+	 *
+	 * @var self
+	 */
+	private static $_instance = null;
+
+	/**
+	 * Implement singleton.
+	 *
+	 * @return self
+	 */
+	public static function get_instance(): self {
+		if ( ! is_a( self::$_instance, __CLASS__ ) ) {
+			self::$_instance = new self();
+			self::$_instance->_setup();
+		}
+
+		return self::$_instance;
+	}
+
+	/**
+	 * Silence is golden!
+	 */
+	private function __construct() {
+		// Add nothing here.
+	}
+
+	/**
+	 * Register hooks.
+	 *
+	 * @return void
+	 */
+	abstract function _setup(): void;
+}