{"id":327,"date":"2020-08-04T23:27:53","date_gmt":"2020-08-04T15:27:53","guid":{"rendered":"http:\/\/123.57.164.21\/?p=327"},"modified":"2020-08-05T12:17:09","modified_gmt":"2020-08-05T04:17:09","slug":"swift-where%e5%85%b3%e9%94%ae%e5%ad%97%e8%af%a6%e8%a7%a3","status":"publish","type":"post","link":"https:\/\/92it.top\/?p=327","title":{"rendered":"Swift where\u5173\u952e\u5b57\u8be6\u89e3"},"content":{"rendered":"\n<p><strong>\u5728Swift\u8bed\u6cd5\u91ccwhere\u5173\u952e\u5b57\u7684\u4f5c\u7528\u8ddfSQL\u7684where\u4e00\u6837\uff0c \u5373\u9644\u52a0\u6761\u4ef6\u5224\u65ad\u3002<\/strong><\/p>\n\n\n\n<pre class=\"wp-block-preformatted\">1. \u7528\u5728do catch\u91cc\u9762<\/pre>\n\n\n\n<pre class=\"EnlighterJSRAW\" data-enlighter-language=\"generic\" data-enlighter-theme=\"\" data-enlighter-highlight=\"\" data-enlighter-linenumbers=\"\" data-enlighter-lineoffset=\"\" data-enlighter-title=\"\" data-enlighter-group=\"\">enum ExceptionError:Error{\n    case httpCode(Int)\n}\nfunc throwError() throws {\n    throw ExceptionError.httpCode(500)\n}\n\/\/do catch\ndo{\n    try throwError()\n}catch ExceptionError.httpCode(let httpCode) where httpCode >= 500{\n    print(\"server error\")\n}\n<\/pre>\n\n\n\n<pre class=\"wp-block-preformatted\">2. \u7528\u5728switch\u91cc\u9762<\/pre>\n\n\n\n<pre class=\"EnlighterJSRAW\" data-enlighter-language=\"generic\" data-enlighter-theme=\"\" data-enlighter-highlight=\"\" data-enlighter-linenumbers=\"\" data-enlighter-lineoffset=\"\" data-enlighter-title=\"\" data-enlighter-group=\"\">\/\/switch\nvar value:(Int,String) = (1,\"\u5c0f\u660e\")\nswitch value {\ncase let (x,y) where x &lt; 60:\n    print(\"\u4e0d\u53ca\u683c\")\ndefault:\n    print(\"\u53ca\u683c\")\n}<\/pre>\n\n\n\n<pre class=\"wp-block-preformatted\">3. for in<\/pre>\n\n\n\n<pre class=\"EnlighterJSRAW\" data-enlighter-language=\"generic\" data-enlighter-theme=\"\" data-enlighter-highlight=\"\" data-enlighter-linenumbers=\"\" data-enlighter-lineoffset=\"\" data-enlighter-title=\"\" data-enlighter-group=\"\">\/\/ for in\nlet arrayOne = [1,2,3,4,5]\nlet dictionary = [1:\"hehe1\",2:\"hehe2\"]\nfor i in arrayOne where dictionary[i] != nil {\n    print(i)\n}<\/pre>\n\n\n\n<pre class=\"wp-block-preformatted\">4. \u4e0e\u8303\u578b\u7ed3\u5408<\/pre>\n\n\n\n<pre class=\"EnlighterJSRAW\" data-enlighter-language=\"generic\" data-enlighter-theme=\"\" data-enlighter-highlight=\"\" data-enlighter-linenumbers=\"\" data-enlighter-lineoffset=\"\" data-enlighter-title=\"\" data-enlighter-group=\"\">\/\/\u7b2c\u4e00\u79cd\u5199\u6cd5\n\/\/ \u5728\u4f7f\u7528\u6cdb\u578b\u7684\u65f6\u5019\u4e5f\u5e38\u5e38\u7528\u5230where\u5bf9\u6cdb\u578b\u52a0\u4ee5\u9650\u5236\nfunc genericFunction&lt;S>(str:S) where S:ExpressibleByStringLiteral{\n    print(str)\n}\n\/\/\u7b2c\u4e8c\u79cd\u5199\u6cd5\nfunc genericFunction&lt;S:ExpressibleByStringLiteral>(str:S){\n    print(str)\n}<\/pre>\n\n\n\n<pre class=\"wp-block-preformatted\">5. \u4e0e\u534f\u8bae\u7ed3\u5408<\/pre>\n\n\n\n<pre class=\"EnlighterJSRAW\" data-enlighter-language=\"generic\" data-enlighter-theme=\"\" data-enlighter-highlight=\"\" data-enlighter-linenumbers=\"\" data-enlighter-lineoffset=\"\" data-enlighter-title=\"\" data-enlighter-group=\"\">protocol SomeProtocol {\n    func someMethod()\n}\n \nclass A: SomeProtocol {\n    let a = 1\n    \n    func someMethod() {\n       print(\"call someMethod\")\n    }\n}\n \nclass B {\n    let a = 2\n}\n \n\/\/\u57fa\u7c7bA\u7ee7\u627f\u4e86SomeProtocol\u534f\u8bae\u624d\u80fd\u6dfb\u52a0\u6269\u5c55\nextension SomeProtocol where Self: A {\n    func showParamA() {\n        print(self.a)\n    }\n}\n\/\/\u53cd\u4f8b\uff0c\u4e0d\u7b26\u5408where\u6761\u4ef6\nextension SomeProtocol where Self: B {\n    func showParamA() {\n        print(self.a)\n    }\n}\nlet objA = A()\nlet objB = B()  \/\/\u7c7bB\u6ca1\u5b9e\u73b0SomeProtocol\uff0c \u6240\u6709\u6ca1\u6709\u534f\u8bae\u65b9\u6cd5\nobjA.showParamA()  \/\/\u8f93\u51fa1<\/pre>\n","protected":false},"excerpt":{"rendered":"<p>\u5728Swift\u8bed\u6cd5\u91ccwhere\u5173\u952e\u5b57\u7684\u4f5c\u7528\u8ddfSQL\u7684where\u4e00\u6837\uff0c \u5373\u9644\u52a0\u6761\u4ef6\u5224\u65ad\u3002 1. \u7528\u5728do catc [&hellip;]<\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"closed","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[8],"tags":[],"_links":{"self":[{"href":"https:\/\/92it.top\/index.php?rest_route=\/wp\/v2\/posts\/327"}],"collection":[{"href":"https:\/\/92it.top\/index.php?rest_route=\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/92it.top\/index.php?rest_route=\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/92it.top\/index.php?rest_route=\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/92it.top\/index.php?rest_route=%2Fwp%2Fv2%2Fcomments&post=327"}],"version-history":[{"count":3,"href":"https:\/\/92it.top\/index.php?rest_route=\/wp\/v2\/posts\/327\/revisions"}],"predecessor-version":[{"id":330,"href":"https:\/\/92it.top\/index.php?rest_route=\/wp\/v2\/posts\/327\/revisions\/330"}],"wp:attachment":[{"href":"https:\/\/92it.top\/index.php?rest_route=%2Fwp%2Fv2%2Fmedia&parent=327"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/92it.top\/index.php?rest_route=%2Fwp%2Fv2%2Fcategories&post=327"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/92it.top\/index.php?rest_route=%2Fwp%2Fv2%2Ftags&post=327"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}