{"id":1413,"date":"2022-11-19T14:55:01","date_gmt":"2022-11-19T06:55:01","guid":{"rendered":"http:\/\/175.24.184.226\/?p=1413"},"modified":"2022-11-19T14:55:46","modified_gmt":"2022-11-19T06:55:46","slug":"go%e7%9a%84derfer","status":"publish","type":"post","link":"\/?p=1413","title":{"rendered":"go\u7684derfer"},"content":{"rendered":"

\u6982\u8ff0<\/h4>\n

defer\u4e00\u822c\u7528\u4e8e\u8d44\u6e90\u7684\u91ca\u653e\u548c\u5f02\u5e38\u7684\u6355\u6349, \u4f5c\u4e3aGo\u8bed\u8a00\u7684\u7279\u6027\u4e4b\u4e00.<\/p>\n

defer \u8bed\u53e5\u4f1a\u5c06\u5176\u540e\u9762\u8ddf\u968f\u7684\u8bed\u53e5\u8fdb\u884c\u5ef6\u8fdf\u5904\u7406. \u610f\u601d\u5c31\u662f\u8bf4 \u8ddf\u5728defer\u540e\u9762\u7684\u8bed\u8a00 \u5c06\u4f1a\u5728\u7a0b\u5e8f\u8fdb\u884c\u6700\u540e\u7684return\u4e4b\u540e\uff08\u5f53\u524d\u51fd\u6570\u6267\u884c\u5b8c\u6bd5\u540e\uff09\u518d\u6267\u884c.<\/p>\n

\u5728 defer \u5f52\u5c5e\u7684\u51fd\u6570\u5373\u5c06\u8fd4\u56de\u65f6\uff0c\u5c06\u5ef6\u8fdf\u5904\u7406\u7684\u8bed\u53e5\u6309 defer \u7684\u9006\u5e8f\u8fdb\u884c\u6267\u884c\uff0c\u4e5f\u5c31\u662f\u8bf4\uff0c\u5148\u88ab defer \u7684\u8bed\u53e5\u6700\u540e\u88ab\u6267\u884c\uff0c\u6700\u540e\u88ab defer \u7684\u8bed\u53e5\uff0c\u6700\u5148\u88ab\u6267\u884c\u3002<\/p>\n

1.\u8d44\u6e90\u7684\u91ca\u653e<\/h4>\n

\u4e00\u822c\u6211\u4eec\u5199\u8bfb\u53d6\u6587\u4ef6\u7684\u4ee3\u7801\u5982\u4e0b\uff1a<\/p>\n

func CopyFile(dstName, srcName string) (written int64, err error) {\n    src, err := os.Open(srcName)\n    if err != nil {\n        return\n    }\n    dst, err := os.Create(dstName)\n    if err != nil {\n        return \n    }\n    dst.Close()\n    src.Close()\n    return\n}<\/code><\/pre>\n
\u5728\u7a0b\u5e8f\u6700\u5f00\u59cb\uff0cos.Open\u53caos.Create\u6253\u5f00\u4e86\u4e24\u4e2a\u6587\u4ef6\u8d44\u6e90\u63cf\u8ff0\u7b26\uff0c\u5e76\u5728\u6700\u540e\u901a\u8fc7file.Close\u65b9\u6cd5\u5f97\u5230\u91ca\u653e\uff0c\u5728\u6b63\u5e38\u60c5\u51b5\u4e0b\uff0c\u8be5\u7a0b\u5e8f\u80fd\u6b63\u5e38\u8fd0\u884c\uff0c\u4e00\u65e6\u5728dstName\u6587\u4ef6\u521b\u5efa\u8fc7\u7a0b\u4e2d\u51fa\u73b0\u9519\u8bef\uff0c\u7a0b\u5e8f\u5c31\u76f4\u63a5\u8fd4\u56de\uff0csrc\u8d44\u6e90\u5c06\u5f97\u4e0d\u5230\u91ca\u653e\u3002\u56e0\u6b64\u9700\u8981\u5728\u6240\u6709\u9519\u8bef\u9000\u51fa\u65f6\u91ca\u653e\u8d44\u6e90\uff0c\u5373\u4fee\u6539\u4e3a\u5982\u4e0b\u4ee3\u7801\u624d\u80fd\u4fdd\u8bc1\u5176\u5728\u5f02\u5e38\u60c5\u51b5\u4e0b\u7684\u6b63\u786e\u6027\u3002<\/p>\n
\n
\u5373\u5728\u6bcf\u4e2aerr\u91cc\u9762\u5982\u679c\u53d1\u751f\u4e86\u5f02\u5e38, \u8981\u53ca\u65f6\u5173\u95edsrc\u7684\u8d44\u6e90.
\n\u8fd9\u4e2a\u95ee\u9898\u51fa\u73b0\u5728\u52a0\u9501\u4e2d\u4e5f\u975e\u5e38\u5e38\u89c1<\/p>\n
l.lock()\n\n\/\/ \u5982\u679c\u4e0b\u9762\u53d1\u751f\u4e86\u5f02\u5e38\n\/\/ \u6211\u4eec\u9700\u8981\u5728\u6bcf\u4e2aerr\u5904\u7406\u5757\u4e2d\u90fd\u52a0\u5165l.unlock()\u6765\u89e3\u9501\n\/\/ \u4e0d\u7136\u8d44\u6e90\u5c31\u5f97\u4e0d\u5230\u91ca\u653e, \u5c31\u4f1a\u4ea7\u751f\u6b7b\u9501\nif err != nil {\n    l.unlock()\n    return\n}<\/code><\/pre>\n
\u4f46\u662f\u8fd9\u6837\u505a\u672a\u514d\u592a\u9ebb\u70e6\u4e86, defer\u4f18\u96c5\u7684\u5e2e\u6211\u4eec\u89e3\u51b3\u4e86\u8fd9\u4e2a\u95ee\u9898
\n\u6bd4\u5982\u6211\u4eec\u53ef\u4ee5\u8fd9\u6837<\/p>\n
src, err := os.Open(srcName)\ndefer src.Close()\nif err != nil {\n    return\n}\ndst, err := os.Create(dstName)\ndefer dst.Close()\nif err != nil {\n    return \n}\n------------------------------------------\nl.lock()\ndefer l.unlock()\n......\nif err != nil {\n    return \n}\n......<\/code><\/pre>\n
\u8fd9\u6837\u5199\u7684\u8bdd, \u5c31\u4e0d\u9700\u8981\u5728\u6bcf\u4e2a\u5f02\u5e38\u5904\u7406\u5757\u4e2d\u90fd\u52a0\u4e0aClose() \u6216\u8005 unlock()\u8bed\u53e5\u4e86.<\/p>\n
2. \u5f02\u5e38\u7684\u6355\u6349<\/h4>\n
\u7a0b\u5e8f\u5728\u8fd0\u884c\u65f6\u53ef\u80fd\u5728\u4efb\u610f\u7684\u5730\u65b9\u53d1\u751fpanic\u5f02\u5e38\uff0c\u4f8b\u5982\u7b97\u672f\u96640\u9519\u8bef\u3001\u5185\u5b58\u65e0\u6548\u8bbf\u95ee\u3001\u6570\u7ec4\u8d8a\u754c\u7b49\uff0c\u8fd9\u4e9b\u9519\u8bef\u4f1a\u5bfc\u81f4\u7a0b\u5e8f\u5f02\u5e38\u9000\u51fa\u3002\u5728\u5f88\u591a\u65f6\u5019\uff0c\u6211\u4eec\u5e0c\u671b\u80fd\u591f\u6355\u83b7\u8fd9\u6837\u7684\u9519\u8bef\uff0c\u540c\u65f6\u5e0c\u671b\u7a0b\u5e8f\u80fd\u591f\u7ee7\u7eed\u6b63\u5e38\u6267\u884c\u3002\u4e00\u4e9b\u8bed\u8a00\u91c7\u7528try\u2026catch\u8bed\u6cd5\uff0c\u5f53try\u5757\u4e2d\u53d1\u751f\u5f02\u5e38\u65f6\uff0c\u53ef\u4ee5\u901a\u8fc7catch\u5757\u6355\u83b7\u3002<\/p>\n
Go\u8bed\u8a00\u4f7f\u7528\u4e86\u7279\u522b\u7684\u65b9\u5f0f\u5904\u7406\u8fd9\u4e00\u95ee\u9898\u3002defer\u7684\u7279\u6027\u662f\u65e0\u8bba\u540e\u7eed\u51fd\u6570\u7684\u6267\u884c\u8def\u5f84\u5982\u4f55\u4ee5\u53ca\u662f\u5426\u53d1\u751f\u4e86panic\uff0c\u5728\u51fd\u6570\u7ed3\u675f\u540e\u4e00\u5b9a\u4f1a\u5f97\u5230\u6267\u884c\uff0c\u8fd9\u4e3a\u5f02\u5e38\u6355\u83b7\u63d0\u4f9b\u4e86\u5f88\u597d\u7684\u65f6\u673a\u3002\u5f02\u5e38\u6355\u83b7\u901a\u5e38\u7ed3\u5408recover\u51fd\u6570\u4e00\u8d77\u4f7f\u7528\u3002<\/p>\n
package main\n\nimport "fmt"\nfunc executePanic(){\n    defer fmt.Println("defer func")\n    panic("This is Pancic Situation")\n    fmt.Println("The function executes Completely")\n}\n\nfunc main(){\n    executePanic()\n    fmt.Println("Main block is executed completely...")\n}<\/code><\/pre>\n
\u5982\u4e0a\u6240\u793a\uff0c\u5728executePanic\u51fd\u6570\u4e2d\uff0c\u624b\u52a8\u6267\u884cpanic\u51fd\u6570\u89e6\u53d1\u4e86\u5f02\u5e38\u3002\u5f53\u5f02\u5e38\u89e6\u53d1\u540e\uff0c\u51fd\u6570\u4ecd\u7136\u4f1a\u8c03\u7528defer\u4e2d\u7684\u51fd\u6570\uff0c\u7136\u540e\u5f02\u5e38\u9000\u51fa\u3002\u8f93\u51fa\u5982\u4e0b\uff0c\u8868\u660e\u8c03\u7528\u4e86defer\u4e2d\u7684\u51fd\u6570\uff0c\u5e76\u4e14main\u51fd\u6570\u5c06\u4e0d\u80fd\u6b63\u5e38\u8fd0\u884c\uff0c\u7a0b\u5e8f\u5f02\u5e38\u9000\u51fa\u6253\u5370\u51fa\u6808\u8ffd\u8e2a\u4fe1\u606f\u3002<\/p>\n
\"image-20221119133945279\" <\/p>\n
\u5982\u4e0b\u6240\u793a\uff0c\u5f53\u5728defer\u51fd\u6570\u4e2d\u4f7f\u7528recover\u8fdb\u884c\u5f02\u5e38\u6355\u83b7\u540e\uff0c\u7a0b\u5e8f\u5c06\u4e0d\u4f1a\u5f02\u5e38\u9000\u51fa\uff0c\u5e76\u4e14\u80fd\u591f\u6267\u884c\u6b63\u5e38\u7684\u51fd\u6570\u6d41\u7a0b\u3002\u5982\u4e0b\u8f93\u51fa\u8868\u660e\uff0c\u5c3d\u7ba1\u6709panic\uff0cmain\u51fd\u6570\u4ecd\u7136\u5728\u6b63\u5e38\u6267\u884c\u540e\u9000\u51fa<\/p>\n
package main\n\nimport "fmt"\n\nfunc executePanic(){\n    defer func(){\n        if err := recover(); err != nil{\n            fmt.Println(err)\n        }\n    }()\n    panic("This is Pancic Situation")\n    fmt.Println("The function executes Completely")\n}\n\nfunc main(){\n    executePanic()\n    fmt.Println("Main block is executed completely...")\n}<\/code><\/pre>\n
\u4f7f\u7528\u4e86recover\u51fd\u6570\u540e, \u7a0b\u5e8f\u5c06\u4e0d\u4f1a\u5f02\u5e38\u9000\u51fa, \u4ecd\u4f1a\u6b63\u5e38\u6267\u884c<\/p>\n
\"image-20221119140118358\" <\/p>\n
3.\u591a\u4e2adefer\u8bed\u53e5\u7684\u6267\u884c\u987a\u5e8f<\/h4>\n
\u5f53\u6709\u591a\u4e2a defer \u884c\u4e3a\u88ab\u6ce8\u518c\u65f6\uff0c\u5b83\u4eec\u4f1a\u4ee5\u9006\u5e8f\u6267\u884c\uff08\u7c7b\u4f3c\u6808\uff0c\u5373\u540e\u8fdb\u5148\u51fa\uff09, \u76f8\u5f53\u4e8e\u5f00\u8f9f\u4e86\u4e00\u4e2a\u5ef6\u65f6\u8c03\u7528\u6808<\/p>\n
func main() {\n    fmt.Println("defer begin")\n    \/\/ \u5c06defer\u653e\u5165\u5ef6\u8fdf\u8c03\u7528\u6808\n    defer fmt.Println(1)\n    defer fmt.Println(2)\n    \/\/ \u6700\u540e\u4e00\u4e2a\u653e\u5165, \u4f4d\u4e8e\u6808\u9876, \u6700\u5148\u8c03\u7528\n    defer fmt.Println(3)\n    fmt.Println("defer end")\n}<\/code><\/pre>\n
\u6267\u884c\u7684\u7ed3\u679c\u5c31\u662f<\/p>\n
\"image-20221119140318219\" <\/p>\n
4.defer\u6267\u884c\u65f6\u7684\u62f7\u8d1d<\/h4>\n
package main\n\nimport "fmt"\n\nfunc main(){\n    test := func(){\n        fmt.Println("test1")\n    }\n    defer test()\n    test = func(){\n        fmt.Println("test2")\n    }\n    fmt.Println("test3")\n}<\/code><\/pre>\n
\u8fd0\u884c\u7ed3\u679c\uff1a<\/p>\n
\"image-20221119140938627\" <\/p>\n
\n
package main\n\nimport "fmt"\n\nfunc main(){\n    x := 10\n    defer func(a int){\n        fmt.Println(a)\n    }(x)\n    x++\n}<\/code><\/pre>\n
\u51fd\u6570\u548c\u53d8\u91cf\u7684\u503c\u90fd\u88ab\u538b\u5165\u6808\u4e2d<\/p>\n
\u8fd0\u884c\u7ed3\u679c\uff1a<\/p>\n
\"image-20221119141204252\" <\/p>\n
\u6362\u4e00\u79cd\u95ed\u5305\u51fd\u6570\u7684\u65b9\u5f0f\uff1a<\/p>\n
 package main\n\n import \"fmt\"\n\n func main(){\n     x := 10\n     defer func(){\n         fmt.Println(x)\n     }()\n     x++\n }<\/code><\/pre>\n
\u7ed3\u679c\u5374\u662f11.<\/p>\n
\u6b64\u5904\u7684defer\u51fd\u6570\u5e76\u6ca1\u6709\u53c2\u6570\uff0c\u5185\u90e8\u4f7f\u7528\u7684\u53d8\u91cf\u7684\u503c\u662f\u5168\u5c40\u7684\u503c\uff0c\u6ca1\u6709\u88ab\u538b\u6808<\/p>\n
5.\u6307\u9488\u76f8\u5173<\/h4>\n
package main\n\nimport "fmt"\n\nfunc main(){\n    x := 10\n    defer func(a *int){\n        fmt.Println(*a)\n    }(&x)\n    x++\n}<\/code><\/pre>\n
\"image-20221119141530896\" <\/p>\n
\u4e3a\u4ec0\u4e48\u8fd0\u884c\u7ed3\u679c\u662f11\u5462\uff1f<\/p>\n
x++,\u6307\u9488\u6307\u5411\u6539\u53d8\u4e86\uff0c\u539f\u672cdefer\u538b\u6808\u7684\u503c\u662f\u6307\u9488\uff0c\u6307\u9488\u6ca1\u6709\u53d1\u751f\u53d8\u5316\uff0c\u4f46\u662f\u6307\u9488\u7684\u6307\u5411\u7684\u503c\u53d8\u4e86\uff0c\u8fd9\u662fdefer\u540e\u9762\u7684\u51fd\u6570\u6240\u4e0d\u77e5\u7684<\/p>\n
6.return\u548cdefer\u7684\u6267\u884c\u987a\u5e8f<\/h4>\n
package main\n\nimport "fmt"\n\nfunc f1() int {\n    x := 10\n    defer func(){\n        x++\n    }()\n    return x\n}\nfunc main(){\n    fmt.Println(f1())\n}<\/code><\/pre>\n
\u8fd0\u884c\u7ed3\u679c\uff1a<\/p>\n
\"image-20221119142706711\" <\/p>\n
\u5176\u5b9e\u8fd9\u4e2a\u4e5f\u662f\u503c\u4f20\u9012<\/p>\n
\u5173\u4e8e\u5f15\u7528\u4f20\u9012\uff1a<\/p>\n
package main\n\nimport "fmt"\n\nfunc f1() *int {\n    a := 10\n    b := &a\n    defer func(){\n        *b++\n    }()\n    return b\n}\nfunc main(){\n    fmt.Println(*f1())\n}<\/code><\/pre>\n
\"image-20221119145114139\" <\/p>\n
\u603b\u7ed3<\/h4>\n
defer\u672c\u8d28\u4e0a\u5e02\u6ce8\u518c\u4e86\u4e00\u4e2a\u5ef6\u8fdf\u51fd\u6570\uff0cdefer\u51fd\u6570\u7684\u6267\u884c\u987a\u5e8f\u5df2\u7ecf\u786e\u5b9a\u4e86<\/p>\n
defer\u6ca1\u6709\u5d4c\u5957\uff0cdefer\u7684\u673a\u5236\u662f\u8981\u53d6\u4ee3try,excpt,finally<\/code><\/p>\n","protected":false},"excerpt":{"rendered":"
\u6982\u8ff0 defer\u4e00\u822c\u7528\u4e8e\u8d44\u6e90\u7684\u91ca\u653e\u548c\u5f02\u5e38\u7684\u6355\u6349, \u4f5c\u4e3aGo\u8bed\u8a00\u7684\u7279\u6027\u4e4b\u4e00. defer \u8bed\u53e5\u4f1a\u5c06\u5176\u540e\u9762\u8ddf\u968f\u7684\u8bed\u53e5\u8fdb\u884c\u5ef6\u8fdf\u5904\u7406. \u610f\u601d\u5c31\u662f   \u2026 …<\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"ngg_post_thumbnail":0},"categories":[117],"tags":[118,113],"_links":{"self":[{"href":"\/index.php?rest_route=\/wp\/v2\/posts\/1413"}],"collection":[{"href":"\/index.php?rest_route=\/wp\/v2\/posts"}],"about":[{"href":"\/index.php?rest_route=\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"\/index.php?rest_route=\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"\/index.php?rest_route=%2Fwp%2Fv2%2Fcomments&post=1413"}],"version-history":[{"count":2,"href":"\/index.php?rest_route=\/wp\/v2\/posts\/1413\/revisions"}],"predecessor-version":[{"id":1415,"href":"\/index.php?rest_route=\/wp\/v2\/posts\/1413\/revisions\/1415"}],"wp:attachment":[{"href":"\/index.php?rest_route=%2Fwp%2Fv2%2Fmedia&parent=1413"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"\/index.php?rest_route=%2Fwp%2Fv2%2Fcategories&post=1413"},{"taxonomy":"post_tag","embeddable":true,"href":"\/index.php?rest_route=%2Fwp%2Fv2%2Ftags&post=1413"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}