{"id":45,"date":"2023-12-19T15:40:55","date_gmt":"2023-12-19T07:40:55","guid":{"rendered":"http:\/\/blog.thirdbody.cn\/?p=45"},"modified":"2026-05-13T11:25:48","modified_gmt":"2026-05-13T03:25:48","slug":"%e6%b5%85%e6%9e%90swift-optional","status":"publish","type":"post","link":"http:\/\/blog.thirdbody.cn\/index.php\/2023\/12\/19\/%e6%b5%85%e6%9e%90swift-optional\/","title":{"rendered":"swift\u7cfb\u5217(\u4e00)\uff1a\u6d45\u6790swift optional"},"content":{"rendered":"

1.\u4e3a\u4ec0\u4e48\u4f7f\u7528optional<\/h3>\n

\u7531\u4e8eswift\u8bed\u8a00\u662f\u7c7b\u578b\u5b89\u5168\u7684\uff0c\u5373\u5728\u521d\u59cb\u5316\u53d8\u91cf\u6216\u5e38\u91cf\u65f6\uff0c\u4e0d\u80fd\u5c06\u5176\u8d4b\u503c\u4e3anil<\/strong>\uff0c\u5426\u5219\u4f1a\u62a5\u9519\uff1a<\/p>\n

var a = nil<\/code><\/pre>\n
\"\"<\/p>\n
\u7136\u800c\uff0c\u6211\u4eec\u5728\u5b9a\u4e49\u53d8\u91cf\u65f6\u5e76\u4e0d\u4e00\u5b9a\u8981\u521d\u59cb\u5316\uff0c\u51fd\u6570\u7684\u8fd4\u56de\u503c\u5e76\u4e0d\u4e00\u5b9a\u6709\u5177\u4f53\u7684\u503c\uff0c\u8fd9\u5c31\u4e3a\u6211\u4eec\u4f7f\u7528\u53d8\u91cf\u5e26\u4e86\u4e0d\u4fbf\uff0c\u6545swift\u63d0\u4f9b\u4e86optional\uff0c\u5373\u53ef\u9009\u7c7b\u578b\uff0c\u6765\u7f13\u89e3\u8fd9\u4e2a\u95ee\u9898\u3002<\/p>\n
\u53ef\u9009\u7c7b\u578b\uff0c\u987e\u540d\u601d\u4e49\u5373\u4f7f\u7528\u8be5\u7c7b\u578b\u7684\u58f0\u660e\u7684\u53d8\u91cf\u53ef\u4ee5\u6709\u503c\uff0c\u4ea6\u53ef\u4ee5\u6ca1\u6709\u503c(nil)\u3002<\/p>\n
2.optional\u7684\u4f7f\u7528<\/h3>\n
\u5728swift\u4e2d\uff0c\u5728\u58f0\u660e\u53d8\u91cf\u7684\u7c7b\u578b\u540e\u9762\u52a0\u4e0a?<\/code>\u5373\u53ef\u7533\u660e\u53ef\u9009\u7c7b\u578b\uff1a<\/p>\n
var str: String? = "abc"<\/code><\/pre>\n
\u7531\u4e8e\u53ef\u9009\u7c7b\u578b\u53d8\u91cf\u7684\u503c\u6709\u53ef\u80fd\u4e3anil<\/code>\uff0c\u6545\u4e0d\u80fd\u76f4\u63a5\u4f7f\u7528\uff0c\u5728swift\u4e2d\uff0c\u4e3b\u8981\u6709\u4ee5\u4e0b\u56db\u79cd\u65b9\u5f0f\u4f7f\u7528optional<\/code>:<\/p>\n
    \n
  • \n
    optional\u62c6\u5305<\/p>\n
    var str: String? = \"abc\"\nprint(str!.count) \/\/ \u4f7f\u7528!\u8fdb\u884c\u62c6\u5305<\/code><\/pre>\n
    \"\"<\/p>\n<\/li>\n
  • \n
    optional\u9690\u5f0f\u62c6\u5305<\/p>\n
    var str: String? = \"abc\"\nprint(str!.count)<\/code><\/pre>\n
    \"\"<\/p>\n<\/li>\n
  • \n
    optional binding<\/p>\n
    var str: String? = \"abc\"\nif let realStr = atr {\nprint(realStr.count)\n}<\/code><\/pre>\n
    \"\"<\/p>\n<\/li>\n
  • \n
    optional\u9009\u62e9\u94fe<\/p>\n
    var str: String? = \"abc\"\nlet count = str?.count    \/\/ count\u4ecd\u662f\u53ef\u9009\u7c7b\u578b\n\/\/ \u5bf9count\u4f7f\u7528\u62c6\u5305\u65b9\u5f0f\u8fdb\u884c\u8bbf\u95ee\nif count != nil {\nlet lastIndex = count! - 1\nprint(lastIndex)\n}<\/code><\/pre>\n
    \"\"<\/p>\n<\/li>\n<\/ul>\n
    3.optional\u539f\u7406\u6d45\u6790<\/h3>\n
    optional\u5e76\u4e0d\u662fswift\u8bed\u8a00\u672c\u8eab\u5e26\u6709\u7684\u7279\u6027\uff0c\u800c\u662f\u901a\u8fc7\u679a\u4e3e\u5b9e\u73b0\u7684\uff0c\u4e0b\u56fe\u662fswift\u6e90\u7801\u622a\u56fe<\/p>\n
    \"\"<\/p>\n
    \u6211\u4eec\u53ef\u4ee5\u901a\u8fc7\u5982\u4e0b\u65b9\u5f0f\u5b9a\u4e49\u53ef\u9009\u7c7b\u578b\uff0c\u5176\u6548\u679c\u5b8c\u5168\u7b49\u540c\u4e8e\u4e0a\u8ff0\u4f7f\u7528?<\/code>\u7684\u65b9\u5f0f<\/p>\n
    var str: Optional<String> = "abc"\nif let realStr = str {\n  print(realStr)\n}<\/code><\/pre>\n
    \"\"<\/p>\n
    \u6211\u4eec\u8fd8\u53ef\u4ee5\u4f7f\u7528Optional<\/code>\u6cdb\u578b\u63d0\u4f9b\u7684unsafelyUnwrapped<\/code>\u65b9\u6cd5\u8fdb\u884c\u89e3\u5305\uff1a<\/p>\n
    var str: Optional<String> = "abc"\nlet count = str.unsafelyUnwrapped.count\nprint(count)<\/code><\/pre>\n
    \"\"<\/p>\n","protected":false},"excerpt":{"rendered":"
    1.\u4e3a\u4ec0\u4e48\u4f7f\u7528optional \u7531\u4e8eswift\u8bed\u8a00\u662f\u7c7b\u578b\u5b89\u5168\u7684\uff0c\u5373\u5728\u521d\u59cb\u5316\u53d8\u91cf\u6216\u5e38\u91cf\u65f6\uff0c\u4e0d\u80fd\u5c06\u5176\u8d4b\u503c\u4e3anil\uff0c […]<\/p>\n","protected":false},"author":1,"featured_media":46,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[19],"tags":[21,20,22],"class_list":["post-45","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-swift","tag-optional","tag-swift","tag-22"],"_links":{"self":[{"href":"http:\/\/blog.thirdbody.cn\/index.php\/wp-json\/wp\/v2\/posts\/45","targetHints":{"allow":["GET"]}}],"collection":[{"href":"http:\/\/blog.thirdbody.cn\/index.php\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"http:\/\/blog.thirdbody.cn\/index.php\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"http:\/\/blog.thirdbody.cn\/index.php\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"http:\/\/blog.thirdbody.cn\/index.php\/wp-json\/wp\/v2\/comments?post=45"}],"version-history":[{"count":2,"href":"http:\/\/blog.thirdbody.cn\/index.php\/wp-json\/wp\/v2\/posts\/45\/revisions"}],"predecessor-version":[{"id":122,"href":"http:\/\/blog.thirdbody.cn\/index.php\/wp-json\/wp\/v2\/posts\/45\/revisions\/122"}],"wp:featuredmedia":[{"embeddable":true,"href":"http:\/\/blog.thirdbody.cn\/index.php\/wp-json\/wp\/v2\/media\/46"}],"wp:attachment":[{"href":"http:\/\/blog.thirdbody.cn\/index.php\/wp-json\/wp\/v2\/media?parent=45"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"http:\/\/blog.thirdbody.cn\/index.php\/wp-json\/wp\/v2\/categories?post=45"},{"taxonomy":"post_tag","embeddable":true,"href":"http:\/\/blog.thirdbody.cn\/index.php\/wp-json\/wp\/v2\/tags?post=45"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}