{"id":196,"date":"2016-05-14T01:35:24","date_gmt":"2016-05-13T17:35:24","guid":{"rendered":"https:\/\/wangqf.com\/?p=196"},"modified":"2016-05-14T01:35:24","modified_gmt":"2016-05-13T17:35:24","slug":"go-channel","status":"publish","type":"post","link":"https:\/\/wangqf.com\/?p=196","title":{"rendered":"Go channel"},"content":{"rendered":"<h2>Channel types<\/h2>\n<p>channel \u7c7b\u578b\u901a\u8fc7\u53d1\u9001\u548c\u63a5\u53d7\u7279\u5b9a\u7c7b\u578b\u7684\u503c\uff0c\u4e3a\u5e76\u884c\u6267\u884c\u51fd\u6570\u63d0\u4f9b\u4e00\u79cd\u901a\u4fe1\u673a\u5236\u3002 channel\u662f\u5148\u8fdb\u5148\u51fa\u7c7b\u578b\u7684\u7ba1\u9053\uff0c\u9ed8\u8ba4\u60c5\u51b5\u4e0b\uff0c\u5728\u53e6\u4e00\u7aef\u51c6\u5907\u597d\u4e4b\u524d\uff0c\u53d1\u9001\u548c\u63a5\u6536\u90fd\u4f1a\u963b\u585e\u3002\u8fd9\u4f7f\u5f97 goroutine \u53ef\u4ee5\u5728\u6ca1\u6709\u660e\u786e\u7684\u9501\u6216\u7ade\u6001\u53d8\u91cf\u7684\u60c5\u51b5\u4e0b\u8fdb\u884c\u540c\u6b65\u3002<\/p>\n<pre class=\"ebnf\">ChannelType = ( \"chan\" | \"chan\" \"&lt;-\" | \"&lt;-\" \"chan\" ) \n<\/pre>\n<p>\u7bad\u5934\u662f\u7ba1\u9053\u7684\u65b9\u5411\uff0c\u53d1\u9001\u6216\u63a5\u6536\uff0c\u5982\u679c\u6ca1\u6709\u6307\u5b9a\u65b9\u5411\uff0c\u7ba1\u9053\u662f\u53cc\u5411\u7684\u3002\u4e00\u4e2achannel\u53ef\u80fd\u53d7\u9650\u4e8e\u53ea\u80fd\u53d1\u9001\u6216\u63a5\u6536\u3002<\/p>\n<pre>chan T          \/\/ can be used to send and receive values of type T\nchan&lt;- float64  \/\/ can only be used to send float64s\n&lt;-chan int      \/\/ can only be used to receive ints\n<\/pre>\n<p>The <code>&lt;-<\/code> operator associates with the leftmost <code>chan<\/code> possible:<\/p>\n<pre>chan&lt;- chan int    \/\/ same as chan&lt;- (chan int)\nchan&lt;- &lt;-chan int  \/\/ same as chan&lt;- (&lt;-chan int)\n&lt;-chan &lt;-chan int  \/\/ same as &lt;-chan (&lt;-chan int)\nchan (&lt;-chan int)\n<\/pre>\n<p>channel\u53ef\u4ee5\u4f7f\u7528\u5185\u7f6e\u7684make\u51fd\u6570\u521b\u5efa\u5e76\u521d\u59cb\u5316\uff0cmake\u53c2\u6570\u6307\u5b9a\u7c7b\u578b\u548c\u53ef\u9009\u7684\u5bb9\u91cf\u3002\u672a\u521d\u59cb\u5316\u7684channel\u503c\u4e3anil\u3002<\/p>\n<pre>make(chan int, 100)\n<\/pre>\n<p>\u5bb9\u91cf\uff0c\u6307\u5b9achannel\u7684buffer\u5927\u5c0f\uff0c\u5143\u7d20\u4e2a\u6570\u3002\u5982\u679c\u5bb9\u91cf\u672a\u6307\u5b9a\u6216\u8005\u4e3a0\uff0cchannel\u662f\u6ca1\u6709buffer\u7684\uff0c\u53ea\u6709\u53d1\u9001\u548c\u63a5\u6536\u90fd\u51c6\u5907\u597d\u7684\u65f6\u5019\uff0c\u901a\u4fe1\u6210\u529f\u3002\u5426\u5219\uff0cchannel\u662f\u53ef\u7f13\u51b2\u7684\uff0c\u901a\u4fe1\u4e0d\u963b\u585e\uff0c\u53ea\u8981\u7a7a\u95f4\u4e0d\u4e3a\u7a7a\uff08\u63a5\u53d7\u8005\uff09\uff0c\u6216\u8005\u7a7a\u95f4\u4e0d\u6ee1\uff08\u53d1\u9001\u8005\uff09\u3002\u4f46\u662f\u503c\u4e3anil\u7684channel\u4f1a\u4e00\u76f4\u963b\u585e\u3002<\/p>\n<p>channel\u53ef\u4ee5\u4f7f\u7528\u5185\u7f6e\u51fd\u6570close\u5173\u95ed\u3002 \u63a5\u53d7\u8005\u53ef\u4ee5\u4f7f\u7528\u591a\u503c\u8d4b\u503c\u7684\u65b9\u6cd5\u5224\u65adchannel\u662f\u5426\u5173\u95ed\u3002\u5f53channel\u5173\u95ed\u65f6\uff0cok\u503c\u4e3afalse\u3002<\/p>\n<pre>x, ok = &lt;-ch\nx, ok := &lt;-ch\nvar x, ok = &lt;-ch<\/pre>\n<h2>\u6ce8\u610f<\/h2>\n<ul>\n<li>\u7ed9\u4e00\u4e2a nil channel \u53d1\u9001\u6570\u636e\uff0c\u9020\u6210\u6c38\u8fdc\u963b\u585e<\/li>\n<li>\u4ece\u4e00\u4e2a nil channel \u63a5\u6536\u6570\u636e\uff0c\u9020\u6210\u6c38\u8fdc\u963b\u585e<\/li>\n<li>\u7ed9\u4e00\u4e2a\u5df2\u7ecf\u5173\u95ed\u7684 channel \u53d1\u9001\u6570\u636e\uff0c\u5f15\u8d77 panic<\/li>\n<li>\u4ece\u4e00\u4e2a\u5df2\u7ecf\u5173\u95ed\u7684 channel \u63a5\u6536\u6570\u636e\uff0c\u7acb\u5373\u8fd4\u56de\u4e00\u4e2a\u96f6\u503c<\/li>\n<\/ul>\n<h3 id=\"articleHeader0\">\u7ed9\u4e00\u4e2a nil channel \u53d1\u9001\u6570\u636e\uff0c\u9020\u6210\u6c38\u8fdc\u963b\u585e<\/h3>\n<p>\u8fd9\u7b2c\u4e00\u4e2a\u4f8b\u5b50\u5bf9\u4e8e\u65b0\u6765\u8005\u662f\u6709\u70b9\u5c0f\u60ca\u5947\u7684\uff0c\u5b83\u7ed9\u4e00\u4e2a nil channel \u53d1\u9001\u6570\u636e\uff0c\u9020\u6210\u6c38\u8fdc\u963b\u585e\u3002<\/p>\n<p>\u4ee5\u4e0b\u8fd9\u4e2a\u7a0b\u5e8f\u5c06\u5728\u7b2c5\u884c\u9020\u6210\u6b7b\u9501\uff0c\u56e0\u4e3a\u672a\u521d\u59cb\u5316\u7684 channel \u662f nil \u7684\uff0c\u5176\u503c\u662f\u96f6<\/p>\n<pre>package main\n\nfunc main() {\n        var c chan string\n        c &lt;- \"let's get started\" \/\/ deadlock\n}<\/pre>\n<h3 id=\"articleHeader1\">\u4ece\u4e00\u4e2a nil channel \u63a5\u6536\u6570\u636e\uff0c\u9020\u6210\u6c38\u8fdc\u963b\u585e<\/h3>\n<p>\u7c7b\u4f3c\u7684\uff0c\u4ece\u4e00\u4e2a nil channel \u63a5\u6536\u6570\u636e\uff0c\u4f1a\u9020\u6210\u63a5\u53d7\u8005\u6c38\u8fdc\u963b\u585e\u3002<\/p>\n<pre>package main\n\nimport \"fmt\"\n\nfunc main() {\n        var c chan string\n        fmt.Println(&lt;-c) \/\/ deadlock\n}\n<\/pre>\n<p>\u4e3a\u4ec0\u4e48\u4f1a\u53d1\u751f\u8fd9\u6837\u7684\u60c5\u51b5\uff1f\u4e0b\u9762\u662f\u4e00\u4e2a\u53ef\u80fd\u7684\u89e3\u91ca<\/p>\n<ul>\n<li>channel \u7684 buffer \u7684\u5927\u5c0f\u4e0d\u662f\u7c7b\u578b\u58f0\u660e\u7684\u4e00\u90e8\u5206\uff0c\u56e0\u6b64\u5b83\u5fc5\u987b\u662f channel \u7684\u503c\u7684\u4e00\u90e8\u5206<\/li>\n<li>\u5982\u679c channel \u672a\u88ab\u521d\u59cb\u5316\uff0c\u5b83\u7684 buffer \u7684\u5927\u5c0f\u5c06\u662f0<\/li>\n<li>\u5982\u679c channel \u7684 buffer \u5927\u5c0f\u662f0\uff0c\u90a3\u4e48\u5b83\u5c06\u6ca1\u6709 buffer<\/li>\n<li>\u5982\u679c channel \u6ca1\u6709 buffer\uff0c\u4e00\u4e2a\u53d1\u9001\u5c06\u4f1a\u88ab\u963b\u585e\uff0c\u76f4\u5230\u53e6\u5916\u4e00\u4e2a goroutine \u4e3a\u63a5\u6536\u505a\u597d\u4e86\u51c6\u5907<\/li>\n<li>\u5982\u679c channel \u662f nil \u7684\uff0c\u5e76\u4e14\u63a5\u6536\u8005\u548c\u53d1\u9001\u8005\u6ca1\u6709\u4efb\u4f55\u4ea4\u4e92\uff0c\u4ed6\u4eec\u90fd\u4f1a\u963b\u585e\u7136\u540e\u5728\u5404\u81ea\u7684 channel \u4e2d\u7b49\u5f85\u4ee5\u53ca\u4e0d\u518d\u88ab\u89e3\u9664\u963b\u585e\u72b6\u6001<\/li>\n<\/ul>\n<h3 id=\"articleHeader2\">\u7ed9\u4e00\u4e2a\u5df2\u7ecf\u5173\u95ed\u7684 channel \u53d1\u9001\u6570\u636e\uff0c\u5f15\u8d77 panic<\/h3>\n<p>\u4ee5\u4e0b\u7a0b\u5e8f\u5c06\u6709\u53ef\u80fd panic\uff0c\u56e0\u4e3a\u5728\u5b83\u7684\u5144\u5f1f\u59d0\u59b9\u6709\u65f6\u95f4\u5b8c\u6210\u53d1\u9001\u4ed6\u4eec\u7684\u503c\u4e4b\u524d\uff0c\u8fd9\u7b2c\u4e00\u4e2a goroutine \u5728\u8fbe\u523010\u7684\u65f6\u5019\u5c06\u5173\u95ed channel\u3002<\/p>\n<pre>package main\nimport \"fmt\"\nfunc main() {\n        var c = make(chan int, 100)\n        for i := 0; i &lt; 10; i++ {\n                go func() {\n                        for j := 0; j &lt; 10; j++ {\n                                c &lt;- j\n                        }\n                        close(c)\n                }()\n        }\n        for i := range c {\n                fmt.Println(i)\n        }\n}\n<\/pre>\n<p>\u56e0\u6b64\u4e3a\u4ec0\u4e48\u6ca1\u6709\u4e00\u4e2a close() \u7248\u672c\u80fd\u8ba9\u4f60\u68c0\u6d4b channel \u662f\u5426\u5173\u95ed\uff1f<\/p>\n<pre>if !isClosed(c) {\n        \/\/ c isn't closed, send the value\n        c &lt;- v\n}\n<\/pre>\n<p>\u4f46\u662f\u8fd9\u4e2a\u51fd\u6570\u6709\u4e00\u4e2a\u5185\u5728\u7684\u7ade\u4e89\uff0c\u67d0\u4e2a\u4eba\u53ef\u80fd\u5728\u6211\u4eec\u68c0\u67e5\u5b8c isClosed(c) \u4e4b\u540e\uff0c\u4f46\u662f\u4ee3\u7801\u83b7\u53d6 c &lt;- v \u4e4b\u524d\u5173\u95ed\u8fd9\u4e2a channel\u3002\u5904\u7406\u8fd9\u4e2a\u95ee\u9898\u7684\u65b9\u6cd5\u53c2\u8003<a href=\"https:\/\/blog.golang.org\/pipelines\">Go Concurrency Patterns: Pipelines and cancellation<\/a>\u00a0\u3002<\/p>\n<h3 id=\"articleHeader3\">\u4ece\u4e00\u4e2a\u5df2\u7ecf\u5173\u95ed\u7684 channel \u63a5\u6536\u6570\u636e\uff0c\u7acb\u5373\u8fd4\u56de\u4e00\u4e2a\u96f6\u503c<\/h3>\n<p>\u8fd9\u6700\u540e\u4e00\u4e2a\u793a\u4f8b\u4e0e\u524d\u4e00\u4e2a\u662f\u76f8\u53cd\u7684\uff0c\u4e00\u65e6\u4e00\u4e2a channel \u88ab\u5173\u95ed\uff0c\u5b83\u7684\u6240\u6709\u7684\u503c\u90fd\u4f1a\u4ece buffer \u4e2d\u6d41\u5931\uff0cchannel \u5c06\u7acb\u5373\u8fd4\u56de0\u503c\u3002<\/p>\n<pre>package main\n\nimport \"fmt\"\n\nfunc main() {\n            c := make(chan int, 3)\n            c &lt;- 1\n            c &lt;- 2\n            c &lt;- 3\n            close(c)\n            for i := 0; i &lt; 4; i++ {\n                        fmt.Printf(\"%d \", &lt;-c) \/\/ prints 1 2 3 0\n            }\n}\n<\/pre>\n<p>\u9488\u5bf9\u8fd9\u4e2a\u95ee\u9898\u7684\u6b63\u786e\u7684\u89e3\u51b3\u529e\u6cd5\u662f\u4f7f\u7528 range \u5faa\u73af\u5904\u7406\uff1a<\/p>\n<pre>for v := range c {\n            \/\/ do something with v\n}\n\nfor v, ok := &lt;- c; ok ; v, ok = &lt;- c {\n            \/\/ do something with v\n}\n<\/pre>\n<p>\u8fd9\u4e24\u4e2a\u8bed\u53e5\u5728\u51fd\u6570\u4e2d\u662f\u76f8\u7b49\u7684\uff0c\u5c55\u793a range \u662f\u505a\u4ec0\u4e48\u3002<\/p>\n<p>&nbsp;<\/p>\n<h2>\u53c2\u8003\u6587\u732e\uff1a<\/h2>\n<p>[1]. <a href=\"https:\/\/go-tour-zh.appspot.com\/concurrency\/2\">Go \u6307\u5357\u00a0<\/a><\/p>\n<p>[2].\u00a0<a href=\"https:\/\/segmentfault.com\/a\/1190000000507018\">Go &#8211; Channel \u539f\u7406<\/a><\/p>\n<p>[3].\u00a0<a href=\"https:\/\/golang.org\/ref\/spec#Channel_types\">The Go Programming Language Specification<\/a><\/p>\n","protected":false},"excerpt":{"rendered":"<p>Channel types channel \u7c7b\u578b\u901a\u8fc7\u53d1\u9001\u548c\u63a5\u53d7\u7279\u5b9a\u7c7b\u578b\u7684\u503c\uff0c\u4e3a\u5e76\u884c\u6267\u884c\u51fd\u6570\u63d0\u4f9b\u4e00\u79cd\u901a\u4fe1\u673a\u5236\u3002  &hellip; <a href=\"https:\/\/wangqf.com\/?p=196\" class=\"more-link\">\u7ee7\u7eed\u9605\u8bfb<span class=\"screen-reader-text\">\u201cGo channel\u201d<\/span><\/a><\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[2],"tags":[],"class_list":["post-196","post","type-post","status-publish","format-standard","hentry","category-2"],"_links":{"self":[{"href":"https:\/\/wangqf.com\/index.php?rest_route=\/wp\/v2\/posts\/196","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/wangqf.com\/index.php?rest_route=\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/wangqf.com\/index.php?rest_route=\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/wangqf.com\/index.php?rest_route=\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/wangqf.com\/index.php?rest_route=%2Fwp%2Fv2%2Fcomments&post=196"}],"version-history":[{"count":0,"href":"https:\/\/wangqf.com\/index.php?rest_route=\/wp\/v2\/posts\/196\/revisions"}],"wp:attachment":[{"href":"https:\/\/wangqf.com\/index.php?rest_route=%2Fwp%2Fv2%2Fmedia&parent=196"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/wangqf.com\/index.php?rest_route=%2Fwp%2Fv2%2Fcategories&post=196"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/wangqf.com\/index.php?rest_route=%2Fwp%2Fv2%2Ftags&post=196"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}