{"id":259,"date":"2019-09-25T16:44:45","date_gmt":"2019-09-25T16:44:45","guid":{"rendered":"https:\/\/golangbyexamples.com\/?p=259"},"modified":"2019-11-30T18:24:33","modified_gmt":"2019-11-30T18:24:33","slug":"state-design-pattern-go","status":"publish","type":"post","link":"https:\/\/golangbyexamples.com\/state-design-pattern-go\/","title":{"rendered":"State Design pattern in Go"},"content":{"rendered":"\n<p class=\"has-medium-font-size\">Note: Interested in understanding how all other design patterns can be implemented in GO. Please see this full reference  &#8211; <a href=\"https:\/\/golangbyexamples.com\/all-design-patterns-golang\/\">All Design Patterns in Go (Golang)<\/a><\/p>\n\n\n\n<div id=\"ez-toc-container\" class=\"ez-toc-v2_0_17 counter-hierarchy counter-decimal ez-toc-light-blue\">\n<div class=\"ez-toc-title-container\">\n<p class=\"ez-toc-title\">Table of Contents<\/p>\n<span class=\"ez-toc-title-toggle\"><a class=\"ez-toc-pull-right ez-toc-btn ez-toc-btn-xs ez-toc-btn-default ez-toc-toggle\" style=\"display: none;\"><i class=\"ez-toc-glyphicon ez-toc-icon-toggle\"><\/i><\/a><\/span><\/div>\n<nav><ul class=\"ez-toc-list ez-toc-list-level-1\"><li class=\"ez-toc-page-1 ez-toc-heading-level-2\"><a class=\"ez-toc-link ez-toc-heading-1\" href=\"https:\/\/golangbyexamples.com\/state-design-pattern-go\/#Definition\" title=\"Definition:\">Definition:<\/a><\/li><li class=\"ez-toc-page-1 ez-toc-heading-level-2\"><a class=\"ez-toc-link ez-toc-heading-2\" href=\"https:\/\/golangbyexamples.com\/state-design-pattern-go\/#When_To_Use\" title=\"When To Use\">When To Use<\/a><\/li><li class=\"ez-toc-page-1 ez-toc-heading-level-2\"><a class=\"ez-toc-link ez-toc-heading-3\" href=\"https:\/\/golangbyexamples.com\/state-design-pattern-go\/#UML_Diagram\" title=\"UML Diagram\">UML Diagram<\/a><\/li><li class=\"ez-toc-page-1 ez-toc-heading-level-2\"><a class=\"ez-toc-link ez-toc-heading-4\" href=\"https:\/\/golangbyexamples.com\/state-design-pattern-go\/#Mapping\" title=\"Mapping&nbsp;\">Mapping&nbsp;<\/a><\/li><li class=\"ez-toc-page-1 ez-toc-heading-level-2\"><a class=\"ez-toc-link ez-toc-heading-5\" href=\"https:\/\/golangbyexamples.com\/state-design-pattern-go\/#Explanation\" title=\"Explanation:\">Explanation:<\/a><\/li><li class=\"ez-toc-page-1 ez-toc-heading-level-2\"><a class=\"ez-toc-link ez-toc-heading-6\" href=\"https:\/\/golangbyexamples.com\/state-design-pattern-go\/#Practical_Example\" title=\"Practical Example:\">Practical Example:<\/a><\/li><\/ul><\/nav><\/div>\n<h2 class=\"wp-block-heading\"><span class=\"ez-toc-section\" id=\"Definition\"><\/span><strong>Definition:<\/strong><span class=\"ez-toc-section-end\"><\/span><\/h2>\n\n\n\n<p class=\"has-medium-font-size\">State design pattern is a behavioral design pattern that is based on Finite State Machine. We will explain the State Design Pattern in the context of an example of a Vending Machine. For simplicity, let&#8217;s assume that vending machine only has one type of item or product.&nbsp;Also for simplicity lets assume that a Vending Machine can be in 4 different states<\/p>\n\n\n\n<ol class=\"has-medium-font-size wp-block-list\"><li><strong>hasItem<\/strong><\/li><li><strong>noItem<\/strong><\/li><li><strong>itemRequested<\/strong><\/li><li><strong>hasMoney<\/strong><\/li><\/ol>\n\n\n\n<p class=\"has-medium-font-size\">A vending machine will also have different actions. Again for simplicity lets assume that there are only four actions:<\/p>\n\n\n\n<ol class=\"has-medium-font-size wp-block-list\"><li><strong>Select the item<\/strong><\/li><li><strong>Add the item<\/strong><\/li><li><strong>Insert Money<\/strong><\/li><li><strong>Dispense Item<\/strong><\/li><\/ol>\n\n\n\n<h2 class=\"wp-block-heading\"><span class=\"ez-toc-section\" id=\"When_To_Use\"><\/span><strong>When To Use<\/strong><span class=\"ez-toc-section-end\"><\/span><\/h2>\n\n\n\n<ul class=\"has-medium-font-size wp-block-list\"><li><strong>Use the State design pattern when the object can be in many different states.&nbsp;Depending upon current request the object needs to change its current state<\/strong><ul><li>In the above example, Vending Machine can be in many different states. A Vending Machine will move from one state to another. Let&#8217;s say Vending Machine is in&nbsp;<strong>itemRequested <\/strong>then it will move to&nbsp;<strong>hasMoney <\/strong>state once the action &#8220;Insert Money&#8221; is done<\/li><\/ul><\/li><li>Use when an object will have different responses to the same request depending upon the current state. Using state design pattern here will prevent a lot of conditional statements<ul><li>For example in the case of Vending Machine, if a user is want to purchase an item then the machine will proceed if it is <strong>hasItemState<\/strong> or it will reject if it is in <strong>noItemState<\/strong>. If you notice here that the Vending Machine on the request of purchase of an item gives two different responses depending upon whether it is in&nbsp;<strong>hasItemState <\/strong>or&nbsp;<strong>noItemState.&nbsp; <\/strong>Do notice the vendingMachine.go file below, it doesn&#8217;t have any kind of conditional statement. All the logic is being handled by concrete state implementations.<\/li><\/ul><\/li><\/ul>\n\n\n\n<h2 class=\"wp-block-heading\"><span class=\"ez-toc-section\" id=\"UML_Diagram\"><\/span><strong>UML Diagram<\/strong><span class=\"ez-toc-section-end\"><\/span><\/h2>\n\n\n\n<figure class=\"wp-block-image\"><img loading=\"lazy\" decoding=\"async\" width=\"639\" height=\"271\" src=\"https:\/\/i1.wp.com\/golangbyexamples.com\/wp-content\/uploads\/2019\/09\/State-Design-Pattern-1.jpg?resize=639%2C271&#038;ssl=1\" alt=\"\" class=\"wp-image-260\" srcset=\"https:\/\/i0.wp.com\/golangbyexamples.com\/wp-content\/uploads\/2019\/09\/State-Design-Pattern-1.jpg?w=639&amp;ssl=1 639w, https:\/\/i0.wp.com\/golangbyexamples.com\/wp-content\/uploads\/2019\/09\/State-Design-Pattern-1.jpg?resize=300%2C127&amp;ssl=1 300w\" sizes=\"auto, (max-width: 639px) 100vw, 639px\" data-recalc-dims=\"1\" \/><\/figure>\n\n\n\n<h2 class=\"wp-block-heading\"><span class=\"ez-toc-section\" id=\"Mapping\"><\/span><strong>Mapping&nbsp;<\/strong><span class=\"ez-toc-section-end\"><\/span><\/h2>\n\n\n\n<p class=\"has-medium-font-size\"><br>The below table represents the mapping from the UML diagram actors to actual implementation actors in code.<br><\/p>\n\n\n\n<figure class=\"wp-block-table is-style-stripes\"><table class=\"has-subtle-pale-blue-background-color has-background\"><tbody><tr><td>Context<\/td><td>vendingMachine.go<\/td><\/tr><tr><td>State Interface<\/td><td>state.go<\/td><\/tr><tr><td>Concrete State 1<\/td><td>noItemState.go<\/td><\/tr><tr><td>Concrete State 2<\/td><td>hasItemState.go<\/td><\/tr><tr><td>Concrete State 3<\/td><td>itemRequestedState.go<\/td><\/tr><tr><td>Concrete State 4<\/td><td>hasMoneyState.go<\/td><\/tr><\/tbody><\/table><\/figure>\n\n\n\n<h2 class=\"wp-block-heading\"><span class=\"ez-toc-section\" id=\"Explanation\"><\/span><strong>Explanation:<\/strong><span class=\"ez-toc-section-end\"><\/span><\/h2>\n\n\n\n<ul class=\"has-medium-font-size wp-block-list\"><li>We have an interface &#8220;State&#8221; which defines signatures of functions that represents action in the context of Vending Machine. Below are the actions function signatures<ol><li>addItem(int) error<\/li><li>requestItem() error<\/li><li>insertMoney(money int) error<\/li><li>dispenseItem() error<\/li><\/ol><\/li><li>Each of the concrete state implementations implements all 4 above function and either move to another state on these actions or gives some response.<\/li><li>Each of the concrete state also embeds a pointer to current Vending Machine object so that state transition can happen on that object.<\/li><\/ul>\n\n\n\n<p>Now lets look at code&nbsp;<\/p>\n\n\n\n<h2 class=\"wp-block-heading\"><span class=\"ez-toc-section\" id=\"Practical_Example\"><\/span><strong>Practical Example:<\/strong><span class=\"ez-toc-section-end\"><\/span><\/h2>\n\n\n\n<p class=\"has-medium-font-size\"><strong>vendingMachine.go<\/strong><\/p>\n\n\n\n<pre class=\"wp-block-prismatic-blocks\"><code class=\"language-go\">package main\n\nimport \"fmt\"\n\ntype vendingMachine struct {\n    hasItem       state\n    itemRequested state\n    hasMoney      state\n    noItem        state\n\n    currentState state\n\n    itemCount int\n    itemPrice int\n}\n\nfunc newVendingMachine(itemCount, itemPrice int) *vendingMachine {\n    v := &vendingMachine{\n        itemCount: itemCount,\n        itemPrice: itemPrice,\n    }\n    hasItemState := &hasItemState{\n        vendingMachine: v,\n    }\n    itemRequestedState := &itemRequestedState{\n        vendingMachine: v,\n    }\n    hasMoneyState := &hasMoneyState{\n        vendingMachine: v,\n    }\n    noItemState := &noItemState{\n        vendingMachine: v,\n    }\n\n    v.setState(hasItemState)\n    v.hasItem = hasItemState\n    v.itemRequested = itemRequestedState\n    v.hasMoney = hasMoneyState\n    v.noItem = noItemState\n    return v\n}\n\nfunc (v *vendingMachine) requestItem() error {\n    return v.currentState.requestItem()\n}\n\nfunc (v *vendingMachine) addItem(count int) error {\n    return v.currentState.addItem(count)\n}\n\nfunc (v *vendingMachine) insertMoney(money int) error {\n    return v.currentState.insertMoney(money)\n}\n\nfunc (v *vendingMachine) dispenseItem() error {\n    return v.currentState.dispenseItem()\n}\n\nfunc (v *vendingMachine) setState(s state) {\n    v.currentState = s\n}\n\nfunc (v *vendingMachine) incrementItemCount(count int) {\n    fmt.Printf(\"Adding %d items\\n\", count)\n    v.itemCount = v.itemCount + count\n}<\/code><\/pre>\n\n\n\n<p class=\"has-medium-font-size\"><strong>state.go<\/strong><\/p>\n\n\n\n<pre class=\"wp-block-prismatic-blocks\"><code class=\"language-go\">package main\n\ntype state interface {\n    addItem(int) error\n    requestItem() error\n    insertMoney(money int) error\n    dispenseItem() error\n}<\/code><\/pre>\n\n\n\n<p class=\"has-medium-font-size\"><strong>noItemState.go<\/strong><\/p>\n\n\n\n<pre class=\"wp-block-prismatic-blocks\"><code class=\"language-go\">package main\n\nimport \"fmt\"\n\ntype noItemState struct {\n    vendingMachine *vendingMachine\n}\n\nfunc (i *noItemState) requestItem() error {\n    return fmt.Errorf(\"Item out of stock\")\n}\n\nfunc (i *noItemState) addItem(count int) error {\n    i.vendingMachine.incrementItemCount(count)\n    i.vendingMachine.setState(i.vendingMachine.hasItem)\n    return nil\n}\n\nfunc (i *noItemState) insertMoney(money int) error {\n    return fmt.Errorf(\"Item out of stock\")\n}\nfunc (i *noItemState) dispenseItem() error {\n    return fmt.Errorf(\"Item out of stock\")\n}<\/code><\/pre>\n\n\n\n<p class=\"has-medium-font-size\"><strong>hasItemState.go<\/strong><\/p>\n\n\n\n<pre class=\"wp-block-prismatic-blocks\"><code class=\"language-go\">package main\n\nimport \"fmt\"\n\ntype hasItemState struct {\n    vendingMachine *vendingMachine\n}\n\nfunc (i *hasItemState) requestItem() error {\n    if i.vendingMachine.itemCount == 0 {\n        i.vendingMachine.setState(i.vendingMachine.noItem)\n        return fmt.Errorf(\"No item present\")\n    }\n    fmt.Printf(\"Item requestd\\n\")\n    i.vendingMachine.setState(i.vendingMachine.itemRequested)\n    return nil\n}\n\nfunc (i *hasItemState) addItem(count int) error {\n    fmt.Printf(\"%d items added\\n\", count)\n    i.vendingMachine.incrementItemCount(count)\n    return nil\n}\n\nfunc (i *hasItemState) insertMoney(money int) error {\n    return fmt.Errorf(\"Please select item first\")\n}\nfunc (i *hasItemState) dispenseItem() error {\n    return fmt.Errorf(\"Please select item first\")\n}<\/code><\/pre>\n\n\n\n<p class=\"has-medium-font-size\"><strong>itemRequestedState.go<\/strong><\/p>\n\n\n\n<pre class=\"wp-block-prismatic-blocks\"><code class=\"language-go\">package main\n\nimport \"fmt\"\n\ntype itemRequestedState struct {\n    vendingMachine *vendingMachine\n}\n\nfunc (i *itemRequestedState) requestItem() error {\n    return fmt.Errorf(\"Item already requested\")\n}\n\nfunc (i *itemRequestedState) addItem(count int) error {\n    return fmt.Errorf(\"Item Dispense in progress\")\n}\n\nfunc (i *itemRequestedState) insertMoney(money int) error {\n    if money < i.vendingMachine.itemPrice {\n        fmt.Errorf(\"Inserted money is less. Please insert %d\", i.vendingMachine.itemPrice)\n    }\n    fmt.Println(\"Money entered is ok\")\n    i.vendingMachine.setState(i.vendingMachine.hasMoney)\n    return nil\n}\n\nfunc (i *itemRequestedState) dispenseItem() error {\n    return fmt.Errorf(\"Please insert money first\")\n}<\/code><\/pre>\n\n\n\n<p class=\"has-medium-font-size\"><strong>hasMoneyState.go<\/strong><\/p>\n\n\n\n<pre class=\"wp-block-prismatic-blocks\"><code class=\"language-go\">package main\n\nimport \"fmt\"\n\ntype hasMoneyState struct {\n    vendingMachine *vendingMachine\n}\n\nfunc (i *hasMoneyState) requestItem() error {\n    return fmt.Errorf(\"Item dispense in progress\")\n}\n\nfunc (i *hasMoneyState) addItem(count int) error {\n    return fmt.Errorf(\"Item dispense in progress\")\n}\n\nfunc (i *hasMoneyState) insertMoney(money int) error {\n    return fmt.Errorf(\"Item out of stock\")\n}\n\nfunc (i *hasMoneyState) dispenseItem() error {\n    fmt.Println(\"Dispensing Item\")\n    i.vendingMachine.itemCount = i.vendingMachine.itemCount - 1\n    if i.vendingMachine.itemCount == 0 {\n        i.vendingMachine.setState(i.vendingMachine.noItem)\n    } else {\n        i.vendingMachine.setState(i.vendingMachine.hasItem)\n    }\n    return nil\n}<\/code><\/pre>\n\n\n\n<p class=\"has-medium-font-size\"><strong>main.go<\/strong><\/p>\n\n\n\n<pre class=\"wp-block-prismatic-blocks\"><code class=\"language-go\">package main\n\nimport (\n    \"fmt\"\n    \"log\"\n)\n\nfunc main() {\n    vendingMachine := newVendingMachine(1, 10)\n    err := vendingMachine.requestItem()\n    if err != nil {\n        log.Fatalf(err.Error())\n    }\n    err = vendingMachine.insertMoney(10)\n    if err != nil {\n        log.Fatalf(err.Error())\n    }\n    err = vendingMachine.dispenseItem()\n    if err != nil {\n        log.Fatalf(err.Error())\n    }\n\n    fmt.Println()\n    err = vendingMachine.addItem(2)\n    if err != nil {\n        log.Fatalf(err.Error())\n    }\n\n    fmt.Println()\n\n    err = vendingMachine.requestItem()\n    if err != nil {\n        log.Fatalf(err.Error())\n    }\n\n    err = vendingMachine.insertMoney(10)\n    if err != nil {\n        log.Fatalf(err.Error())\n    }\n\n    err = vendingMachine.dispenseItem()\n    if err != nil {\n        log.Fatalf(err.Error())\n    }\n}<\/code><\/pre>\n\n\n\n<p class=\"has-medium-font-size\"><strong>Output:<\/strong><\/p>\n\n\n\n<pre class=\"wp-block-prismatic-blocks\"><code class=\"language-go\">Item requestd\nMoney entered is ok\nDispensing Item\n\nAdding 2 items\n\nItem requestd\nMoney entered is ok\nDispensing Item<\/code><\/pre>\n","protected":false},"excerpt":{"rendered":"<p>Note: Interested in understanding how all other design patterns can be implemented in GO. Please see this full reference &#8211; All Design Patterns in Go (Golang) Table of Contents Definition:When To UseUML&#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":[26,30,3,4,31,33,32],"class_list":["post-259","post","type-post","status-publish","format-standard","hentry","category-tech","tag-design","tag-designpattern","tag-go","tag-golang","tag-patter","tag-state","tag-state-design-pattern"],"yoast_head":"<!-- This site is optimized with the Yoast SEO plugin v22.7 - https:\/\/yoast.com\/wordpress\/plugins\/seo\/ -->\n<title>State Design pattern 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\/state-design-pattern-go\/\" \/>\n<meta property=\"og:locale\" content=\"en_US\" \/>\n<meta property=\"og:type\" content=\"article\" \/>\n<meta property=\"og:title\" content=\"State Design pattern in Go - Welcome To Golang By Example\" \/>\n<meta property=\"og:description\" content=\"Note: Interested in understanding how all other design patterns can be implemented in GO. Please see this full reference &#8211; All Design Patterns in Go (Golang) Table of Contents Definition:When To UseUML...\" \/>\n<meta property=\"og:url\" content=\"https:\/\/golangbyexamples.com\/state-design-pattern-go\/\" \/>\n<meta property=\"og:site_name\" content=\"Welcome To Golang By Example\" \/>\n<meta property=\"article:published_time\" content=\"2019-09-25T16:44:45+00:00\" \/>\n<meta property=\"article:modified_time\" content=\"2019-11-30T18:24:33+00:00\" \/>\n<meta property=\"og:image\" content=\"https:\/\/golangbyexamples.com\/wp-content\/uploads\/2019\/09\/State-Design-Pattern-1.jpg\" \/>\n<meta name=\"author\" content=\"admin\" \/>\n<meta name=\"twitter:card\" content=\"summary_large_image\" \/>\n<meta name=\"twitter:label1\" content=\"Written by\" \/>\n\t<meta name=\"twitter:data1\" content=\"admin\" \/>\n\t<meta name=\"twitter:label2\" content=\"Est. reading time\" \/>\n\t<meta name=\"twitter:data2\" content=\"5 minutes\" \/>\n<script type=\"application\/ld+json\" class=\"yoast-schema-graph\">{\"@context\":\"https:\/\/schema.org\",\"@graph\":[{\"@type\":\"WebPage\",\"@id\":\"https:\/\/golangbyexamples.com\/state-design-pattern-go\/\",\"url\":\"https:\/\/golangbyexamples.com\/state-design-pattern-go\/\",\"name\":\"State Design pattern in Go - Welcome To Golang By Example\",\"isPartOf\":{\"@id\":\"https:\/\/golangbyexamples.com\/#website\"},\"primaryImageOfPage\":{\"@id\":\"https:\/\/golangbyexamples.com\/state-design-pattern-go\/#primaryimage\"},\"image\":{\"@id\":\"https:\/\/golangbyexamples.com\/state-design-pattern-go\/#primaryimage\"},\"thumbnailUrl\":\"https:\/\/golangbyexamples.com\/wp-content\/uploads\/2019\/09\/State-Design-Pattern-1.jpg\",\"datePublished\":\"2019-09-25T16:44:45+00:00\",\"dateModified\":\"2019-11-30T18:24:33+00:00\",\"author\":{\"@id\":\"https:\/\/golangbyexamples.com\/#\/schema\/person\/8833ea7638dafd763cb1db6c0ca4576f\"},\"breadcrumb\":{\"@id\":\"https:\/\/golangbyexamples.com\/state-design-pattern-go\/#breadcrumb\"},\"inLanguage\":\"en-US\",\"potentialAction\":[{\"@type\":\"ReadAction\",\"target\":[\"https:\/\/golangbyexamples.com\/state-design-pattern-go\/\"]}]},{\"@type\":\"ImageObject\",\"inLanguage\":\"en-US\",\"@id\":\"https:\/\/golangbyexamples.com\/state-design-pattern-go\/#primaryimage\",\"url\":\"https:\/\/golangbyexamples.com\/wp-content\/uploads\/2019\/09\/State-Design-Pattern-1.jpg\",\"contentUrl\":\"https:\/\/golangbyexamples.com\/wp-content\/uploads\/2019\/09\/State-Design-Pattern-1.jpg\"},{\"@type\":\"BreadcrumbList\",\"@id\":\"https:\/\/golangbyexamples.com\/state-design-pattern-go\/#breadcrumb\",\"itemListElement\":[{\"@type\":\"ListItem\",\"position\":1,\"name\":\"Home\",\"item\":\"https:\/\/golangbyexamples.com\/\"},{\"@type\":\"ListItem\",\"position\":2,\"name\":\"State Design pattern in Go\"}]},{\"@type\":\"WebSite\",\"@id\":\"https:\/\/golangbyexamples.com\/#website\",\"url\":\"https:\/\/golangbyexamples.com\/\",\"name\":\"Welcome To Golang By Example\",\"description\":\"\",\"potentialAction\":[{\"@type\":\"SearchAction\",\"target\":{\"@type\":\"EntryPoint\",\"urlTemplate\":\"https:\/\/golangbyexamples.com\/?s={search_term_string}\"},\"query-input\":\"required name=search_term_string\"}],\"inLanguage\":\"en-US\"},{\"@type\":\"Person\",\"@id\":\"https:\/\/golangbyexamples.com\/#\/schema\/person\/8833ea7638dafd763cb1db6c0ca4576f\",\"name\":\"admin\",\"image\":{\"@type\":\"ImageObject\",\"inLanguage\":\"en-US\",\"@id\":\"https:\/\/golangbyexamples.com\/#\/schema\/person\/image\/\",\"url\":\"https:\/\/secure.gravatar.com\/avatar\/?s=96&d=mm&r=g\",\"contentUrl\":\"https:\/\/secure.gravatar.com\/avatar\/?s=96&d=mm&r=g\",\"caption\":\"admin\"},\"url\":\"https:\/\/golangbyexamples.com\/author\/admin\/\"}]}<\/script>\n<!-- \/ Yoast SEO plugin. -->","yoast_head_json":{"title":"State Design pattern in Go - Welcome To Golang By Example","robots":{"index":"index","follow":"follow","max-snippet":"max-snippet:-1","max-image-preview":"max-image-preview:large","max-video-preview":"max-video-preview:-1"},"canonical":"https:\/\/golangbyexamples.com\/state-design-pattern-go\/","og_locale":"en_US","og_type":"article","og_title":"State Design pattern in Go - Welcome To Golang By Example","og_description":"Note: Interested in understanding how all other design patterns can be implemented in GO. Please see this full reference &#8211; All Design Patterns in Go (Golang) Table of Contents Definition:When To UseUML...","og_url":"https:\/\/golangbyexamples.com\/state-design-pattern-go\/","og_site_name":"Welcome To Golang By Example","article_published_time":"2019-09-25T16:44:45+00:00","article_modified_time":"2019-11-30T18:24:33+00:00","og_image":[{"url":"https:\/\/golangbyexamples.com\/wp-content\/uploads\/2019\/09\/State-Design-Pattern-1.jpg"}],"author":"admin","twitter_card":"summary_large_image","twitter_misc":{"Written by":"admin","Est. reading time":"5 minutes"},"schema":{"@context":"https:\/\/schema.org","@graph":[{"@type":"WebPage","@id":"https:\/\/golangbyexamples.com\/state-design-pattern-go\/","url":"https:\/\/golangbyexamples.com\/state-design-pattern-go\/","name":"State Design pattern in Go - Welcome To Golang By Example","isPartOf":{"@id":"https:\/\/golangbyexamples.com\/#website"},"primaryImageOfPage":{"@id":"https:\/\/golangbyexamples.com\/state-design-pattern-go\/#primaryimage"},"image":{"@id":"https:\/\/golangbyexamples.com\/state-design-pattern-go\/#primaryimage"},"thumbnailUrl":"https:\/\/golangbyexamples.com\/wp-content\/uploads\/2019\/09\/State-Design-Pattern-1.jpg","datePublished":"2019-09-25T16:44:45+00:00","dateModified":"2019-11-30T18:24:33+00:00","author":{"@id":"https:\/\/golangbyexamples.com\/#\/schema\/person\/8833ea7638dafd763cb1db6c0ca4576f"},"breadcrumb":{"@id":"https:\/\/golangbyexamples.com\/state-design-pattern-go\/#breadcrumb"},"inLanguage":"en-US","potentialAction":[{"@type":"ReadAction","target":["https:\/\/golangbyexamples.com\/state-design-pattern-go\/"]}]},{"@type":"ImageObject","inLanguage":"en-US","@id":"https:\/\/golangbyexamples.com\/state-design-pattern-go\/#primaryimage","url":"https:\/\/golangbyexamples.com\/wp-content\/uploads\/2019\/09\/State-Design-Pattern-1.jpg","contentUrl":"https:\/\/golangbyexamples.com\/wp-content\/uploads\/2019\/09\/State-Design-Pattern-1.jpg"},{"@type":"BreadcrumbList","@id":"https:\/\/golangbyexamples.com\/state-design-pattern-go\/#breadcrumb","itemListElement":[{"@type":"ListItem","position":1,"name":"Home","item":"https:\/\/golangbyexamples.com\/"},{"@type":"ListItem","position":2,"name":"State Design pattern in Go"}]},{"@type":"WebSite","@id":"https:\/\/golangbyexamples.com\/#website","url":"https:\/\/golangbyexamples.com\/","name":"Welcome To Golang By Example","description":"","potentialAction":[{"@type":"SearchAction","target":{"@type":"EntryPoint","urlTemplate":"https:\/\/golangbyexamples.com\/?s={search_term_string}"},"query-input":"required name=search_term_string"}],"inLanguage":"en-US"},{"@type":"Person","@id":"https:\/\/golangbyexamples.com\/#\/schema\/person\/8833ea7638dafd763cb1db6c0ca4576f","name":"admin","image":{"@type":"ImageObject","inLanguage":"en-US","@id":"https:\/\/golangbyexamples.com\/#\/schema\/person\/image\/","url":"https:\/\/secure.gravatar.com\/avatar\/?s=96&d=mm&r=g","contentUrl":"https:\/\/secure.gravatar.com\/avatar\/?s=96&d=mm&r=g","caption":"admin"},"url":"https:\/\/golangbyexamples.com\/author\/admin\/"}]}},"jetpack_featured_media_url":"","jetpack_publicize_connections":[],"jetpack_sharing_enabled":true,"jetpack_shortlink":"https:\/\/wp.me\/paOs1b-4b","amp_validity":null,"amp_enabled":true,"_links":{"self":[{"href":"https:\/\/golangbyexamples.com\/wp-json\/wp\/v2\/posts\/259","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/golangbyexamples.com\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/golangbyexamples.com\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/golangbyexamples.com\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/golangbyexamples.com\/wp-json\/wp\/v2\/comments?post=259"}],"version-history":[{"count":8,"href":"https:\/\/golangbyexamples.com\/wp-json\/wp\/v2\/posts\/259\/revisions"}],"predecessor-version":[{"id":1037,"href":"https:\/\/golangbyexamples.com\/wp-json\/wp\/v2\/posts\/259\/revisions\/1037"}],"wp:attachment":[{"href":"https:\/\/golangbyexamples.com\/wp-json\/wp\/v2\/media?parent=259"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/golangbyexamples.com\/wp-json\/wp\/v2\/categories?post=259"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/golangbyexamples.com\/wp-json\/wp\/v2\/tags?post=259"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}