{"id":86511,"date":"2026-07-28T20:16:44","date_gmt":"2026-07-28T12:16:44","guid":{"rendered":"https:\/\/www.wsisp.com\/helps\/86511.html"},"modified":"2026-07-28T20:16:44","modified_gmt":"2026-07-28T12:16:44","slug":"kotlin%e4%b8%ad%e5%b1%9e%e6%80%a7%e5%a3%b0%e6%98%8egetter%e3%80%81setter%e3%80%81backing-field","status":"publish","type":"post","link":"https:\/\/www.wsisp.com\/helps\/86511.html","title":{"rendered":"kotlin\u4e2d\u5c5e\u6027\u58f0\u660egetter\u3001setter\u3001backing field"},"content":{"rendered":"

Kotlin \u652f\u6301\u540e\u5907\u5c5e\u6027\u548c\u59d4\u6258\u5c5e\u6027，\u5b83\u4eec\u5141\u8bb8\u4f60\u5728\u4e0d\u76f4\u63a5\u4f7f\u7528\u5b57\u6bb5\u7684\u60c5\u51b5\u4e0b\u7ba1\u7406\u5c5e\u6027\u3002
\n1\u3001\u540e\u5907\u5c5e\u6027<\/p>\n\n\u4fee\u9970\u7b26gettersetterbacking field<\/tr>\n\n\n\n
val<\/td>\n\u2705 \u6709<\/td>\n\u274c \u65e0<\/td>\n\u89c6\u60c5\u51b5\u6709<\/td>\n<\/tr>\n
var<\/td>\n\u2705 \u6709<\/td>\n\u2705 \u6709<\/td>\n\u89c6\u60c5\u51b5\u6709<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n

backing field（\u5e55\u540e\u5b57\u6bb5，\u5373 field）\u53ea\u5728 getter\/setter \u4e2d\u5b9e\u9645\u8bbf\u95ee\u4e86\u5b83\u65f6\u624d\u4f1a\u751f\u6210；\u5982\u679c getter \u662f\u7eaf\u8ba1\u7b97（\u5982 get() = x + 1 \u4e14\u6ca1\u8bfb field），\u7f16\u8bd1\u5668\u5c31\u4e0d\u4f1a\u5206\u914d\u90a3\u4e2a\u5b58\u50a8\u5b57\u6bb5\u3002<\/p>\n

var name: String = ""
\n get() = field \/\/ \u2705 \u8bfb\u90a3\u5757\u5b58\u50a8
\n set(v) { field = v } \/\/ \u2705 \u5199\u90a3\u5757\u5b58\u50a8<\/p>\n

\/\/ field \u53ea\u5728 getter\/setter \u5185\u90e8\u53ef\u7528，\u4e0d\u662f\u5173\u952e\u5b57，\u662f\u4e00\u4e2a\u4e0a\u4e0b\u6587\u76f8\u5173\u7684\u9690\u5f0f\u53d8\u91cf\u3002<\/p>\n

\/\/ var：\u53ef\u540c\u65f6\u5b9a\u4e49 get + set
\nvar name: String = ""
\n get() = field.uppercase()
\n set(value) { field = value.trim() }<\/p>\n

\/\/ val：\u53ea\u80fd\u5b9a\u4e49 get，\u5199 set \u4f1a\u7f16\u8bd1\u9519\u8bef
\nval id: Long = 0L
\n get() = field
\n \/\/ set(v) { … } \/\/ \u274c \u4e0d\u80fd\u5199<\/p>\n\n\u5199\u6cd5\u6709 backing field？\u539f\u56e0<\/tr>\n\n\n\n\n\n\n\n
var x: Int = 0<\/td>\n\u2705<\/td>\nvar \u5fc5\u987b\u80fd\u5b58，\u8981\u5b58\u5c31\u5f97\u6709\u5b57\u6bb5<\/td>\n<\/tr>\n
val x: Int = 0<\/td>\n\u2705<\/td>\nval \u521d\u59cb\u5316\u540e\u503c\u56fa\u5b9a，\u8981\u5b58\u521d\u59cb\u503c<\/td>\n<\/tr>\n
val x: Int get() = 42<\/td>\n\u274c<\/td>\ngetter \u4e0d\u4f9d\u8d56\u4efb\u4f55\u5b58\u50a8，\u7eaf\u8ba1\u7b97<\/td>\n<\/tr>\n
val x: Int get() = y + 1 \/\/ \u6bcf\u6b21\u8bfb\u90fd\u8ba1\u7b97<\/td>\n\u274c<\/td>\n\u540c\u4e0a，\u8bfb\u522b\u4eba\u7684\u5b57\u6bb5<\/td>\n<\/tr>\n
var x: Int = 0; get() = field<\/td>\n\u2705<\/td>\nsetter \u9690\u5f0f\u7528 field，\u5fc5\u987b\u5b58<\/td>\n<\/tr>\n
var x: Int get() = compute(); set(v) { cache = v }<\/td>\n\u274c<\/td>\nget\/set \u90fd\u6ca1\u7528 field，\u6ca1\u5b57\u6bb5<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n

Backing field = \u5c5e\u6027\u80cc\u540e\u90a3\u5757\u771f\u6b63\u88c5\u6570\u636e\u7684\u79c1\u6709\u5b57\u6bb5；field \u662f\u5728 getter\/setter \u5185\u5f15\u7528\u5b83\u7684\u552f\u4e00\u540d\u5b57；\u4e0d\u662f\u6240\u6709\u5c5e\u6027\u90fd\u6709 backing field，\u7eaf\u8ba1\u7b97\u7684\u5c5e\u6027\u548c\u88ab\u59d4\u6258\u7684\u5c5e\u6027\u90fd\u6ca1\u6709\u3002<\/p>\n

class Demo {
\n \/\/ 1. \u6709 backing field
\n var count: Int = 0
\n set(v) { field = if (v < 0) 0 else v } \/\/ \u5199\u5165\u6821\u9a8c<\/p>\n

\/\/ 2. \u65e0 backing field（\u6d3e\u751f\u5c5e\u6027）
\n val isPositive: Boolean get() = count > 0<\/p>\n

\/\/ 3. \u65e0 backing field（\u8f6c\u53d1\u5230\u522b\u7684\u5bf9\u8c61）
\n val displayCount: Int get() = count \/\/ \u6bcf\u6b21\u8bfb count \u7684\u5f53\u524d\u503c<\/p>\n

\/\/ 4. \u6709 backing field（\u9ed8\u8ba4 getter\/setter）
\n val id: Long = System.currentTimeMillis()
\n}<\/p>\n

\u53cd\u7f16\u8bd1\u6210 Java \u540e\u5927\u81f4\u662f：<\/p>\n

class Demo {
\n private int count; \/\/ \u2190 backing field
\n private final long id; \/\/ \u2190 backing field
\n \/\/ isPositive\u3001displayCount \u6ca1\u6709\u5b57\u6bb5，\u53ea\u6709\u65b9\u6cd5<\/p>\n

public int getCount() { return count; }
\n public void setCount(int v) { this.count = v < 0 ? 0 : v; }
\n public boolean isPositive() { return getCount() > 0; }
\n public int getDisplayCount() { return getCount(); } \/\/ get()\u76f8\u5f53\u4e8e\u5b9e\u73b0\u4e86get\u65b9\u6cd5
\n public long getId() { return id; }
\n}<\/p>\n

2\u3001\u59d4\u6258\u5c5e\u6027<\/p>\n

\u59d4\u6258\u5c5e\u6027（\u53e6\u4e00\u79cd\u58f0\u660e\u65b9\u5f0f）\u4f8b\u5982，\u4f7f\u7528by lazy()\u521b\u5efa\u7684\u5c5e\u6027\u5c31\u662f\u4e00\u79cd\u59d4\u6258\u5c5e\u6027，\u5b83\u5728\u7b2c\u4e00\u6b21\u8bbf\u95ee\u65f6\u624d\u8ba1\u7b97\u5176\u503c\u3002<\/p>\n

val x: Int by lazy { compute() }
\nvar y: String by Delegates.observable("") { _, old, new -> … }
\nvar z: String by map \/\/ \u59d4\u6258\u7ed9 Map<\/p>\n

\u7528 by \u628a get\/set \u5b8c\u5168\u4ea4\u7ed9\u59d4\u6258\u5bf9\u8c61，\u6b64\u65f6\u4e0d\u80fd\u5199 get()\/set() \u81ea\u5b9a\u4e49\u5757（\u5df2\u7ecf\u88ab\u59d4\u6258\u63a5\u7ba1）\u3002<\/p>\n","protected":false},"excerpt":{"rendered":"

Kotlin \u652f\u6301\u540e\u5907\u5c5e\u6027\u548c\u59d4\u6258\u5c5e\u6027，\u5b83\u4eec\u5141\u8bb8\u4f60\u5728\u4e0d\u76f4\u63a5\u4f7f\u7528\u5b57\u6bb5\u7684\u60c5\u51b5\u4e0b\u7ba1\u7406\u5c5e\u6027\u3002
\n1\u3001\u540e\u5907\u5c5e\u6027\u4fee\u9970\u7b26gettersetterbacking fieldval\u2705 \u6709\u274c \u65e0\u89c6\u60c5\u51b5\u6709var\u2705 \u6709\u2705 \u6709\u89c6\u60c5\u51b5\u6709backing field（\u5e55\u540e\u5b57\u6bb5，\u5373 field）\u53ea\u5728 getter\/setter \u4e2d\u5b9e\u9645\u8bbf\u95ee\u4e86\u5b83\u65f6\u624d\u4f1a\u751f\u6210；\u5982\u679c getter \u662f\u7eaf\u8ba1\u7b97（\u5982 get() x 1 \u4e14\u6ca1\u8bfb field&<\/p>\n","protected":false},"author":2,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[1],"tags":[84,1693],"topic":[],"class_list":["post-86511","post","type-post","status-publish","format-standard","hentry","category-server","tag-android","tag-kotlin"],"yoast_head":"\nkotlin\u4e2d\u5c5e\u6027\u58f0\u660egetter\u3001setter\u3001backing field - \u7f51\u7855\u4e92\u8054\u5e2e\u52a9\u4e2d\u5fc3<\/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:\/\/www.wsisp.com\/helps\/86511.html\" \/>\n<meta property=\"og:locale\" content=\"zh_CN\" \/>\n<meta property=\"og:type\" content=\"article\" \/>\n<meta property=\"og:title\" content=\"kotlin\u4e2d\u5c5e\u6027\u58f0\u660egetter\u3001setter\u3001backing field - \u7f51\u7855\u4e92\u8054\u5e2e\u52a9\u4e2d\u5fc3\" \/>\n<meta property=\"og:description\" content=\"Kotlin \u652f\u6301\u540e\u5907\u5c5e\u6027\u548c\u59d4\u6258\u5c5e\u6027，\u5b83\u4eec\u5141\u8bb8\u4f60\u5728\u4e0d\u76f4\u63a5\u4f7f\u7528\u5b57\u6bb5\u7684\u60c5\u51b5\u4e0b\u7ba1\u7406\u5c5e\u6027\u3002 1\u3001\u540e\u5907\u5c5e\u6027\u4fee\u9970\u7b26gettersetterbacking fieldval\u2705 \u6709\u274c \u65e0\u89c6\u60c5\u51b5\u6709var\u2705 \u6709\u2705 \u6709\u89c6\u60c5\u51b5\u6709backing field（\u5e55\u540e\u5b57\u6bb5，\u5373 field）\u53ea\u5728 getter\/setter \u4e2d\u5b9e\u9645\u8bbf\u95ee\u4e86\u5b83\u65f6\u624d\u4f1a\u751f\u6210；\u5982\u679c getter \u662f\u7eaf\u8ba1\u7b97（\u5982 get() x 1 \u4e14\u6ca1\u8bfb field&\" \/>\n<meta property=\"og:url\" content=\"https:\/\/www.wsisp.com\/helps\/86511.html\" \/>\n<meta property=\"og:site_name\" content=\"\u7f51\u7855\u4e92\u8054\u5e2e\u52a9\u4e2d\u5fc3\" \/>\n<meta property=\"article:published_time\" content=\"2026-07-28T12:16:44+00:00\" \/>\n<meta name=\"author\" content=\"admin\" \/>\n<meta name=\"twitter:card\" content=\"summary_large_image\" \/>\n<meta name=\"twitter:label1\" content=\"\u4f5c\u8005\" \/>\n\t<meta name=\"twitter:data1\" content=\"admin\" \/>\n\t<meta name=\"twitter:label2\" content=\"\u9884\u8ba1\u9605\u8bfb\u65f6\u95f4\" \/>\n\t<meta name=\"twitter:data2\" content=\"1 \u5206\" \/>\n<script type=\"application\/ld+json\" class=\"yoast-schema-graph\">{\"@context\":\"https:\/\/schema.org\",\"@graph\":[{\"@type\":\"WebPage\",\"@id\":\"https:\/\/www.wsisp.com\/helps\/86511.html\",\"url\":\"https:\/\/www.wsisp.com\/helps\/86511.html\",\"name\":\"kotlin\u4e2d\u5c5e\u6027\u58f0\u660egetter\u3001setter\u3001backing field - \u7f51\u7855\u4e92\u8054\u5e2e\u52a9\u4e2d\u5fc3\",\"isPartOf\":{\"@id\":\"https:\/\/www.wsisp.com\/helps\/#website\"},\"datePublished\":\"2026-07-28T12:16:44+00:00\",\"dateModified\":\"2026-07-28T12:16:44+00:00\",\"author\":{\"@id\":\"https:\/\/www.wsisp.com\/helps\/#\/schema\/person\/358e386c577a3ab51c4493330a20ad41\"},\"breadcrumb\":{\"@id\":\"https:\/\/www.wsisp.com\/helps\/86511.html#breadcrumb\"},\"inLanguage\":\"zh-Hans\",\"potentialAction\":[{\"@type\":\"ReadAction\",\"target\":[\"https:\/\/www.wsisp.com\/helps\/86511.html\"]}]},{\"@type\":\"BreadcrumbList\",\"@id\":\"https:\/\/www.wsisp.com\/helps\/86511.html#breadcrumb\",\"itemListElement\":[{\"@type\":\"ListItem\",\"position\":1,\"name\":\"\u9996\u9875\",\"item\":\"https:\/\/www.wsisp.com\/helps\"},{\"@type\":\"ListItem\",\"position\":2,\"name\":\"kotlin\u4e2d\u5c5e\u6027\u58f0\u660egetter\u3001setter\u3001backing field\"}]},{\"@type\":\"WebSite\",\"@id\":\"https:\/\/www.wsisp.com\/helps\/#website\",\"url\":\"https:\/\/www.wsisp.com\/helps\/\",\"name\":\"\u7f51\u7855\u4e92\u8054\u5e2e\u52a9\u4e2d\u5fc3\",\"description\":\"\u9999\u6e2f\u670d\u52a1\u5668_\u9999\u6e2f\u4e91\u670d\u52a1\u5668\u8d44\u8baf_\u670d\u52a1\u5668\u5e2e\u52a9\u6587\u6863_\u670d\u52a1\u5668\u6559\u7a0b\",\"potentialAction\":[{\"@type\":\"SearchAction\",\"target\":{\"@type\":\"EntryPoint\",\"urlTemplate\":\"https:\/\/www.wsisp.com\/helps\/?s={search_term_string}\"},\"query-input\":\"required name=search_term_string\"}],\"inLanguage\":\"zh-Hans\"},{\"@type\":\"Person\",\"@id\":\"https:\/\/www.wsisp.com\/helps\/#\/schema\/person\/358e386c577a3ab51c4493330a20ad41\",\"name\":\"admin\",\"image\":{\"@type\":\"ImageObject\",\"inLanguage\":\"zh-Hans\",\"@id\":\"https:\/\/www.wsisp.com\/helps\/#\/schema\/person\/image\/\",\"url\":\"https:\/\/gravatar.wp-china-yes.net\/avatar\/?s=96&d=mystery\",\"contentUrl\":\"https:\/\/gravatar.wp-china-yes.net\/avatar\/?s=96&d=mystery\",\"caption\":\"admin\"},\"sameAs\":[\"http:\/\/wp.wsisp.com\"],\"url\":\"https:\/\/www.wsisp.com\/helps\/author\/admin\"}]}<\/script>\n<!-- \/ Yoast SEO plugin. -->","yoast_head_json":{"title":"kotlin\u4e2d\u5c5e\u6027\u58f0\u660egetter\u3001setter\u3001backing field - \u7f51\u7855\u4e92\u8054\u5e2e\u52a9\u4e2d\u5fc3","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:\/\/www.wsisp.com\/helps\/86511.html","og_locale":"zh_CN","og_type":"article","og_title":"kotlin\u4e2d\u5c5e\u6027\u58f0\u660egetter\u3001setter\u3001backing field - \u7f51\u7855\u4e92\u8054\u5e2e\u52a9\u4e2d\u5fc3","og_description":"Kotlin \u652f\u6301\u540e\u5907\u5c5e\u6027\u548c\u59d4\u6258\u5c5e\u6027，\u5b83\u4eec\u5141\u8bb8\u4f60\u5728\u4e0d\u76f4\u63a5\u4f7f\u7528\u5b57\u6bb5\u7684\u60c5\u51b5\u4e0b\u7ba1\u7406\u5c5e\u6027\u3002 1\u3001\u540e\u5907\u5c5e\u6027\u4fee\u9970\u7b26gettersetterbacking fieldval\u2705 \u6709\u274c \u65e0\u89c6\u60c5\u51b5\u6709var\u2705 \u6709\u2705 \u6709\u89c6\u60c5\u51b5\u6709backing field（\u5e55\u540e\u5b57\u6bb5，\u5373 field）\u53ea\u5728 getter\/setter \u4e2d\u5b9e\u9645\u8bbf\u95ee\u4e86\u5b83\u65f6\u624d\u4f1a\u751f\u6210；\u5982\u679c getter \u662f\u7eaf\u8ba1\u7b97（\u5982 get() x 1 \u4e14\u6ca1\u8bfb field&","og_url":"https:\/\/www.wsisp.com\/helps\/86511.html","og_site_name":"\u7f51\u7855\u4e92\u8054\u5e2e\u52a9\u4e2d\u5fc3","article_published_time":"2026-07-28T12:16:44+00:00","author":"admin","twitter_card":"summary_large_image","twitter_misc":{"\u4f5c\u8005":"admin","\u9884\u8ba1\u9605\u8bfb\u65f6\u95f4":"1 \u5206"},"schema":{"@context":"https:\/\/schema.org","@graph":[{"@type":"WebPage","@id":"https:\/\/www.wsisp.com\/helps\/86511.html","url":"https:\/\/www.wsisp.com\/helps\/86511.html","name":"kotlin\u4e2d\u5c5e\u6027\u58f0\u660egetter\u3001setter\u3001backing field - \u7f51\u7855\u4e92\u8054\u5e2e\u52a9\u4e2d\u5fc3","isPartOf":{"@id":"https:\/\/www.wsisp.com\/helps\/#website"},"datePublished":"2026-07-28T12:16:44+00:00","dateModified":"2026-07-28T12:16:44+00:00","author":{"@id":"https:\/\/www.wsisp.com\/helps\/#\/schema\/person\/358e386c577a3ab51c4493330a20ad41"},"breadcrumb":{"@id":"https:\/\/www.wsisp.com\/helps\/86511.html#breadcrumb"},"inLanguage":"zh-Hans","potentialAction":[{"@type":"ReadAction","target":["https:\/\/www.wsisp.com\/helps\/86511.html"]}]},{"@type":"BreadcrumbList","@id":"https:\/\/www.wsisp.com\/helps\/86511.html#breadcrumb","itemListElement":[{"@type":"ListItem","position":1,"name":"\u9996\u9875","item":"https:\/\/www.wsisp.com\/helps"},{"@type":"ListItem","position":2,"name":"kotlin\u4e2d\u5c5e\u6027\u58f0\u660egetter\u3001setter\u3001backing field"}]},{"@type":"WebSite","@id":"https:\/\/www.wsisp.com\/helps\/#website","url":"https:\/\/www.wsisp.com\/helps\/","name":"\u7f51\u7855\u4e92\u8054\u5e2e\u52a9\u4e2d\u5fc3","description":"\u9999\u6e2f\u670d\u52a1\u5668_\u9999\u6e2f\u4e91\u670d\u52a1\u5668\u8d44\u8baf_\u670d\u52a1\u5668\u5e2e\u52a9\u6587\u6863_\u670d\u52a1\u5668\u6559\u7a0b","potentialAction":[{"@type":"SearchAction","target":{"@type":"EntryPoint","urlTemplate":"https:\/\/www.wsisp.com\/helps\/?s={search_term_string}"},"query-input":"required name=search_term_string"}],"inLanguage":"zh-Hans"},{"@type":"Person","@id":"https:\/\/www.wsisp.com\/helps\/#\/schema\/person\/358e386c577a3ab51c4493330a20ad41","name":"admin","image":{"@type":"ImageObject","inLanguage":"zh-Hans","@id":"https:\/\/www.wsisp.com\/helps\/#\/schema\/person\/image\/","url":"https:\/\/gravatar.wp-china-yes.net\/avatar\/?s=96&d=mystery","contentUrl":"https:\/\/gravatar.wp-china-yes.net\/avatar\/?s=96&d=mystery","caption":"admin"},"sameAs":["http:\/\/wp.wsisp.com"],"url":"https:\/\/www.wsisp.com\/helps\/author\/admin"}]}},"_links":{"self":[{"href":"https:\/\/www.wsisp.com\/helps\/wp-json\/wp\/v2\/posts\/86511","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/www.wsisp.com\/helps\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/www.wsisp.com\/helps\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/www.wsisp.com\/helps\/wp-json\/wp\/v2\/users\/2"}],"replies":[{"embeddable":true,"href":"https:\/\/www.wsisp.com\/helps\/wp-json\/wp\/v2\/comments?post=86511"}],"version-history":[{"count":0,"href":"https:\/\/www.wsisp.com\/helps\/wp-json\/wp\/v2\/posts\/86511\/revisions"}],"wp:attachment":[{"href":"https:\/\/www.wsisp.com\/helps\/wp-json\/wp\/v2\/media?parent=86511"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.wsisp.com\/helps\/wp-json\/wp\/v2\/categories?post=86511"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.wsisp.com\/helps\/wp-json\/wp\/v2\/tags?post=86511"},{"taxonomy":"topic","embeddable":true,"href":"https:\/\/www.wsisp.com\/helps\/wp-json\/wp\/v2\/topic?post=86511"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}