{"id":12936,"date":"2024-03-15T01:39:38","date_gmt":"2024-03-15T01:39:38","guid":{"rendered":"https:\/\/www.silicloud.com\/blog\/how-to-apply-the-singleton-design-pattern-in-c\/"},"modified":"2025-08-05T08:57:41","modified_gmt":"2025-08-05T08:57:41","slug":"how-to-apply-the-singleton-design-pattern-in-c","status":"publish","type":"post","link":"https:\/\/www.silicloud.com\/blog\/how-to-apply-the-singleton-design-pattern-in-c\/","title":{"rendered":"Singleton Pattern in C++: Step-by-Step"},"content":{"rendered":"<p>In C++, the following steps can be used to implement the singleton pattern:<\/p>\n<ol>\n<li>Create a class, and set the constructor and destructor as private to prevent other code from directly creating objects.<\/li>\n<li>Declare a pointer to the class object within the private static members of the class, to store the instance of the singleton object.<\/li>\n<li>Provide a static public method to retrieve an instance of the singleton object. The method should first check if the singleton object&#8217;s instance already exists, and if not, create a new instance, store it in a static member, and finally return a pointer to that instance.<\/li>\n<li>One way to ensure only one thread can create an instance in a multi-threaded environment is by using locks.<\/li>\n<li>By defining a private copy constructor and assignment operator function, prevent the creation of new instances through copy constructor and assignment operator functions.<\/li>\n<li>Finally, in the program, you can obtain an instance of the singleton object by calling the static public method and then use that instance for operations.<\/li>\n<\/ol>\n<p>Here is a simple example code of the singleton design pattern.<\/p>\n<pre class=\"post-pre\"><code><span class=\"hljs-keyword\">class<\/span> <span class=\"hljs-title class_\">Singleton<\/span> {\r\n<span class=\"hljs-keyword\">private<\/span>:\r\n    <span class=\"hljs-type\">static<\/span> Singleton* instance; <span class=\"hljs-comment\">\/\/ \u9759\u6001\u6210\u5458\uff0c\u4fdd\u5b58\u5355\u4f8b\u5bf9\u8c61\u7684\u5b9e\u4f8b<\/span>\r\n    <span class=\"hljs-built_in\">Singleton<\/span>() {} <span class=\"hljs-comment\">\/\/ \u79c1\u6709\u6784\u9020\u51fd\u6570<\/span>\r\n\r\n<span class=\"hljs-keyword\">public<\/span>:\r\n    <span class=\"hljs-function\"><span class=\"hljs-type\">static<\/span> Singleton* <span class=\"hljs-title\">getInstance<\/span><span class=\"hljs-params\">()<\/span> <\/span>{\r\n        <span class=\"hljs-keyword\">if<\/span> (instance == <span class=\"hljs-literal\">nullptr<\/span>) {\r\n            instance = <span class=\"hljs-keyword\">new<\/span> <span class=\"hljs-built_in\">Singleton<\/span>();\r\n        }\r\n        <span class=\"hljs-keyword\">return<\/span> instance;\r\n    }\r\n    <span class=\"hljs-comment\">\/\/ \u7981\u6b62\u62f7\u8d1d\u6784\u9020\u51fd\u6570\u548c\u8d4b\u503c\u8fd0\u7b97\u7b26\u51fd\u6570<\/span>\r\n    <span class=\"hljs-built_in\">Singleton<\/span>(<span class=\"hljs-type\">const<\/span> Singleton&amp;) = <span class=\"hljs-keyword\">delete<\/span>;\r\n    Singleton&amp; <span class=\"hljs-keyword\">operator<\/span>=(<span class=\"hljs-type\">const<\/span> Singleton&amp;) = <span class=\"hljs-keyword\">delete<\/span>;\r\n};\r\n\r\nSingleton* Singleton::instance = <span class=\"hljs-literal\">nullptr<\/span>; <span class=\"hljs-comment\">\/\/ \u5bf9\u9759\u6001\u6210\u5458\u8fdb\u884c\u521d\u59cb\u5316<\/span>\r\n\r\n<span class=\"hljs-function\"><span class=\"hljs-type\">int<\/span> <span class=\"hljs-title\">main<\/span><span class=\"hljs-params\">()<\/span> <\/span>{\r\n    Singleton* singleton1 = Singleton::<span class=\"hljs-built_in\">getInstance<\/span>();\r\n    Singleton* singleton2 = Singleton::<span class=\"hljs-built_in\">getInstance<\/span>();\r\n    \r\n    <span class=\"hljs-keyword\">if<\/span> (singleton1 == singleton2) {\r\n        cout &lt;&lt; <span class=\"hljs-string\">\"\u4e24\u4e2a\u5bf9\u8c61\u662f\u540c\u4e00\u4e2a\u5b9e\u4f8b\"<\/span> &lt;&lt; endl;\r\n    }\r\n    <span class=\"hljs-keyword\">else<\/span> {\r\n        cout &lt;&lt; <span class=\"hljs-string\">\"\u4e24\u4e2a\u5bf9\u8c61\u4e0d\u662f\u540c\u4e00\u4e2a\u5b9e\u4f8b\"<\/span> &lt;&lt; endl;\r\n    }\r\n    \r\n    <span class=\"hljs-keyword\">return<\/span> <span class=\"hljs-number\">0<\/span>;\r\n}\r\n<\/code><\/pre>\n<p>In the above code, the Singleton class&#8217;s singleton object instance is obtained by calling the Singleton::getInstance() method, and then comparing the two pointers to determine if they are the same instance.<\/p>\n","protected":false},"excerpt":{"rendered":"<p>In C++, the following steps can be used to implement the singleton pattern: Create a class, and set the constructor and destructor as private to prevent other code from directly creating objects. Declare a pointer to the class object within the private static members of the class, to store the instance of the singleton object. [&hellip;]<\/p>\n","protected":false},"author":6,"featured_media":0,"comment_status":"closed","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"_import_markdown_pro_load_document_selector":0,"_import_markdown_pro_submit_text_textarea":"","footnotes":""},"categories":[1],"tags":[4763,381,10307,438,12721],"class_list":["post-12936","post","type-post","status-publish","format-standard","hentry","category-uncategorized","tag-c-tutorials","tag-c-programming","tag-design-patterns","tag-object-oriented-programming","tag-singleton-pattern"],"yoast_head":"<!-- This site is optimized with the Yoast SEO Premium plugin v21.5 (Yoast SEO v21.5) - https:\/\/yoast.com\/wordpress\/plugins\/seo\/ -->\n<title>Singleton Pattern in C++: Step-by-Step - Blog - Silicon Cloud<\/title>\n<meta name=\"description\" content=\"Learn how to implement the singleton design pattern in C++. 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