{"id":825,"date":"2019-12-10T19:33:05","date_gmt":"2019-12-10T19:33:05","guid":{"rendered":"https:\/\/golangbyexamples.com\/?p=825"},"modified":"2019-12-10T19:33:18","modified_gmt":"2019-12-10T19:33:18","slug":"empty-struct-in-go","status":"publish","type":"post","link":"https:\/\/golangbyexamples.com\/empty-struct-in-go\/","title":{"rendered":"Empty struct in GO"},"content":{"rendered":"\n<p class=\"has-medium-font-size\">Empty struct <strong>struct{} <\/strong>in GO doesn&#8217;t occupy any memory. It is of zero byte. <\/p>\n\n\n\n<p class=\"has-medium-font-size\">Below are some of the uses of empty struct<\/p>\n\n\n\n<ul class=\"has-medium-font-size wp-block-list\"><li>Useful for creating implementations that require no data. <\/li><\/ul>\n\n\n\n<p class=\"has-medium-font-size\">Eg. One example is in while implementing Null Object Design Pattern in Go. The Null object doesn&#8217;t have any data. See an example of Null Object Design Pattern in GO &#8211; <a href=\"https:\/\/golangbyexamples.com\/null-object-design-pattern-golang\/\">https:\/\/golangbyexamples.com\/null-object-design-pattern-golang\/<\/a><br><\/p>\n\n\n\n<ul class=\"has-medium-font-size wp-block-list\"><li>Empty struct also a very good use case in a channel when you only want to use a channel for notification and not for actually passing in any data.<\/li><\/ul>\n\n\n\n<p class=\"has-medium-font-size\">Eg: In context package of GO we have <strong>cancelCtx<\/strong> which is represented as below. See done channel is using an empty struct as it is only used for notifying cancellation and has no data value.<\/p>\n\n\n\n<pre class=\"wp-block-prismatic-blocks\"><code class=\"language-go\">type cancelCtx struct {\n    Context\n    mu       sync.Mutex            \/\/ protects following fields\n    done     chan struct{}         \/\/ created lazily, closed by first cancel call\n    children map[canceler]struct{} \/\/ set to nil by the first cancel call\n    err      error                 \/\/ set to non-nil by the first cancel call\n}<\/code><\/pre>\n\n\n\n<ul class=\"has-medium-font-size wp-block-list\"><li>Implementation of Set data structure. A set is a data structure that holds elements without any particular order. An element only appears once in a set. We use map[keyType]struct{} for set. struct{} is only just to let us know if an element exists in the set or not.<\/li><\/ul>\n\n\n\n<p class=\"has-medium-font-size\">See this link for set implementation in golang &#8211; <a href=\"https:\/\/golangbyexamples.com\/set-implementation-in-golang\/\">https:\/\/golangbyexamples.com\/set-implementation-in-golang\/<\/a><br><\/p>\n\n\n\n<ul class=\"has-medium-font-size wp-block-list\"><li>Perfect replacement for a channel of Boolean. A boolean does occupy some space as struct does not, hence more efficient to use a channel of struct{}. See below example<\/li><\/ul>\n\n\n\n<pre class=\"wp-block-prismatic-blocks\"><code class=\"language-go\">package main\n\nimport (\n    \"fmt\"\n    \"time\"\n)\n\nfunc main() {\n    done := make(chan struct{}, 4)\n    for i := 0; i < 4; i++ {\n        go runasync(done)\n    }\n    for i := 0; i < 4; i++ {\n        <-done\n    }\n    close(done)\n    fmt.Printf(\"Finish\")\n}\n\nfunc runasync(done chan<- struct{}) {\n    time.Sleep(1 * time.Second)\n    done <- struct{}{}\n    return\n}<\/code><\/pre>\n","protected":false},"excerpt":{"rendered":"<p>Empty struct struct{} in GO doesn&#8217;t occupy any memory. It is of zero byte. Below are some of the uses of empty struct Useful for creating implementations that require no data. Eg&#8230;.<\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"spay_email":"","footnotes":"","jetpack_publicize_message":"","jetpack_is_tweetstorm":false},"categories":[1],"tags":[],"class_list":["post-825","post","type-post","status-publish","format-standard","hentry","category-tech"],"yoast_head":"<!-- This site is optimized with the Yoast SEO plugin v22.7 - https:\/\/yoast.com\/wordpress\/plugins\/seo\/ -->\n<title>Empty struct in GO - Welcome To Golang By Example<\/title>\n<meta name=\"robots\" content=\"index, follow, max-snippet:-1, max-image-preview:large, max-video-preview:-1\" \/>\n<link rel=\"canonical\" href=\"https:\/\/golangbyexamples.com\/empty-struct-in-go\/\" \/>\n<meta property=\"og:locale\" content=\"en_US\" \/>\n<meta property=\"og:type\" content=\"article\" \/>\n<meta property=\"og:title\" content=\"Empty struct in GO - Welcome To Golang By Example\" \/>\n<meta property=\"og:description\" content=\"Empty struct struct{} in GO doesn&#8217;t occupy any memory. 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