From 1b5fe57b9fa551da3f59aad70b2eeb138c93d563 Mon Sep 17 00:00:00 2001
From: cloud <psws@qq.com>
Date: Fri, 15 Apr 2022 04:27:54 +0800
Subject: [PATCH] =?UTF-8?q?=E5=8D=95=E4=BE=8B=E6=A8=A1=E5=BC=8F?=
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---
 demo/Creational/Singleton/Run.php             | 41 +++++++++++++++++
 demo/Creational/Singleton/Singleton.php       | 45 +++++++++++++++++++
 .../Singleton/Tests/SingletonTest.php         | 20 +++++++++
 3 files changed, 106 insertions(+)
 create mode 100644 demo/Creational/Singleton/Run.php
 create mode 100644 demo/Creational/Singleton/Singleton.php
 create mode 100644 demo/Creational/Singleton/Tests/SingletonTest.php

diff --git a/demo/Creational/Singleton/Run.php b/demo/Creational/Singleton/Run.php
new file mode 100644
index 0000000..1ffa60d
--- /dev/null
+++ b/demo/Creational/Singleton/Run.php
@@ -0,0 +1,41 @@
+<?php
+
+namespace demo\Creational\Singleton;
+
+class Run extends \bin\Design
+{
+    
+    /**
+     * 单例模式被公认为是 反面模式，为了获得更好的可测试性和可维护性，请使用『依赖注入模式』。
+     *
+     * [反面模式]：在软件工程中，一个反面模式（Anti-pattern 或 Antipattern）指的是在实践中明显出现但又低效或是有待优化的设计模式，
+     * 是用来解决问题的带有共同性的不良方法。它们已经经过研究并分类，以防止日后重蹈覆辙，并能在研发尚未投产的系统时辨认出来。
+     *
+     * @inheritDoc
+     */
+    public function setDesignName() : string
+    {
+        return '单例模式（Singleton）';
+    }
+    
+    /**
+     * @inheritDoc
+     */
+    public function setDesignRefUrl() : string
+    {
+        return 'https://learnku.com/docs/php-design-patterns/2018/Singleton/1494';
+    }
+    
+    /**
+     * @inheritDoc
+     */
+    public function main()
+    {
+        $firstCall  = Singleton::getInstance();
+        $secondCall = Singleton::getInstance();
+        // 判断类型是否一致
+        dump(Singleton::class instanceof $firstCall);
+        // 判断是否一样
+        dump($firstCall === $secondCall);
+    }
+}
\ No newline at end of file
diff --git a/demo/Creational/Singleton/Singleton.php b/demo/Creational/Singleton/Singleton.php
new file mode 100644
index 0000000..12f17fa
--- /dev/null
+++ b/demo/Creational/Singleton/Singleton.php
@@ -0,0 +1,45 @@
+<?php
+
+namespace demo\Creational\Singleton;
+
+final class Singleton
+{
+    /**
+     * @var Singleton
+     */
+    private static $instance;
+    
+    /**
+     * 通过懒加载获得实例（在第一次使用的时候创建）
+     */
+    public static function getInstance(): Singleton
+    {
+        if (null === static::$instance) {
+            static::$instance = new static();
+        }
+        
+        return static::$instance;
+    }
+    
+    /**
+     * 不允许从外部调用以防止创建多个实例
+     * 要使用单例，必须通过 Singleton::getInstance() 方法获取实例
+     */
+    private function __construct()
+    {
+    }
+    
+    /**
+     * 防止实例被克隆（这会创建实例的副本）
+     */
+    private function __clone()
+    {
+    }
+    
+    /**
+     * 防止反序列化（这将创建它的副本）
+     */
+    public function __wakeup()
+    {
+    }
+}
\ No newline at end of file
diff --git a/demo/Creational/Singleton/Tests/SingletonTest.php b/demo/Creational/Singleton/Tests/SingletonTest.php
new file mode 100644
index 0000000..4c81603
--- /dev/null
+++ b/demo/Creational/Singleton/Tests/SingletonTest.php
@@ -0,0 +1,20 @@
+<?php
+
+namespace demo\Creational\Singleton\Tests;
+
+use demo\Creational\Singleton\Singleton;
+use PHPUnit\Framework\TestCase;
+
+class SingletonTest extends TestCase
+{
+    public function testUniqueness()
+    {
+        $firstCall  = Singleton::getInstance();
+        $secondCall = Singleton::getInstance();
+        
+        // 断言变量属于给定类型
+        $this->assertInstanceOf(Singleton::class, $firstCall);
+        // 断言两个变量具有相同的类型和值。 用于对象，它断言两个变量引用同一个对象
+        $this->assertSame($firstCall, $secondCall);
+    }
+}
\ No newline at end of file