{"id":796,"date":"2019-12-01T13:52:08","date_gmt":"2019-12-01T13:52:08","guid":{"rendered":"https:\/\/golangbyexamples.com\/?p=796"},"modified":"2019-12-01T13:52:17","modified_gmt":"2019-12-01T13:52:17","slug":"go-check-if-type-implements-interface","status":"publish","type":"post","link":"https:\/\/golangbyexamples.com\/go-check-if-type-implements-interface\/","title":{"rendered":"Go : Check if type implements an interface"},"content":{"rendered":"\n<p class=\"has-medium-font-size\">Sometimes there can be scenarios where it is needed to know if your type satisfies an interface or not. This can be easily achieved using a blank identifier.<\/p>\n\n\n\n<pre class=\"wp-block-prismatic-blocks\"><code class=\"language-go\">package main\n\ntype shape interface {\n    getNumSides() int\n    getArea() int\n}\n\ntype square struct {\n    len int\n}\n\nfunc (s square) getNumSides() int {\n    return 4\n}\n\n\/\/ func (s square) getArea() int {\n\/\/  return s.len * 2\n\/\/ }\n\nfunc main() {\n    \/\/Verify that *square implement shape\n    var _ shape = square{}\n}<\/code><\/pre>\n\n\n\n<p class=\"has-medium-font-size\">In the above program, we have commented out the square&#8217;s <strong>getArea() <\/strong>function. On &#8220;go build&#8221; above program gives the error<\/p>\n\n\n\n<pre class=\"wp-block-prismatic-blocks\"><code class=\"language-go\">main.go:25:6: cannot use square literal (type square) as type shape in assignment:\n        square does not implement shape (missing getArea method)<\/code><\/pre>\n\n\n\n<p class=\"has-medium-font-size\">On uncommenting the <strong>getArea() <\/strong>method the error goes away. To check if a pointer of the type implements the interface then it can be done as below<\/p>\n\n\n\n<pre class=\"wp-block-prismatic-blocks\"><code class=\"language-go\">var _ shape = &square{}<\/code><\/pre>\n\n\n\n<p><strong>OR<\/strong><\/p>\n\n\n\n<pre class=\"wp-block-prismatic-blocks\"><code class=\"language-go\">var _ shape = (*square)(nil)<\/code><\/pre>\n\n\n\n<p class=\"has-medium-font-size\">First one will give the error <\/p>\n\n\n\n<pre class=\"wp-block-prismatic-blocks\"><code class=\"language-go\">main.go:25:6: cannot use (*square)(nil) (type *square) as type shape in assignment:\n        *square does not implement shape (missing getArea method)<\/code><\/pre>\n\n\n\n<p class=\"has-medium-font-size\">while the latter one will give error <\/p>\n\n\n\n<pre class=\"wp-block-prismatic-blocks\"><code class=\"language-go\">main.go:25:6: cannot use &square literal (type *square) as type shape in assignment:\n        *square does not implement shape (missing getArea method)<\/code><\/pre>\n","protected":false},"excerpt":{"rendered":"<p>Sometimes there can be scenarios where it is needed to know if your type satisfies an interface or not. This can be easily achieved using a blank identifier. In the above program,&#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":[3,11,99],"class_list":["post-796","post","type-post","status-publish","format-standard","hentry","category-tech","tag-go","tag-interface","tag-type"],"yoast_head":"<!-- This site is optimized with the Yoast SEO plugin v22.7 - https:\/\/yoast.com\/wordpress\/plugins\/seo\/ -->\n<title>Go : Check if type implements an interface - 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\/go-check-if-type-implements-interface\/\" \/>\n<meta property=\"og:locale\" content=\"en_US\" \/>\n<meta property=\"og:type\" content=\"article\" \/>\n<meta property=\"og:title\" content=\"Go : Check if type implements an interface - Welcome To Golang By Example\" \/>\n<meta property=\"og:description\" content=\"Sometimes there can be scenarios where it is needed to know if your type satisfies an interface or not. 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