Tomemos, por ejemplo, un marco de trabajo o una biblioteca que está diseñando para otros usuarios, estos usuarios eventualmente tendrán un main function
código para ejecutar su aplicación. Si el usuario importa directamente un subpaquete del proyecto de su biblioteca, entonces init
se llamará a ese subpaquete ( una vez ) en primer lugar. Lo mismo para el paquete raíz de la biblioteca, etc.
Hay muchas ocasiones en las que puede desear que se ejecute un bloque de código sin la existencia de a main func
, directamente o no.
Si usted, como desarrollador de la biblioteca imaginaria, importa el subpaquete de su biblioteca que tiene una init
función, se llamará primero y , una vez , no tiene un main func
pero necesita asegurarse de que algunas variables o una tabla, se inicializará antes de las llamadas de otras funciones.
Una cosa buena para recordar y no para preocuparse, es que:
el init
siempre ejecutará una vez por aplicación.
init
la ejecución ocurre:
- justo antes de la
init
función del paquete "llamador",
- antes del, opcionalmente
main func
,
- pero después de las variables a nivel de paquete,
var = [...] or cost = [...]
,
Cuando importe un paquete, ejecutará todas sus funciones de inicio, por orden .
Daré un muy buen ejemplo de una función init. Agregará tipos MIME a una biblioteca de go estándar denominada mime
y una función de nivel de paquete utilizará el mime
paquete estándar directamente para obtener los tipos MIME personalizados que ya se han inicializado en su init
función:
package mime
import (
"mime"
"path/filepath"
)
var types = map[string]string{
".3dm": "x-world/x-3dmf",
".3dmf": "x-world/x-3dmf",
".7z": "application/x-7z-compressed",
".a": "application/octet-stream",
".aab": "application/x-authorware-bin",
".aam": "application/x-authorware-map",
".aas": "application/x-authorware-seg",
".abc": "text/vndabc",
".ace": "application/x-ace-compressed",
".acgi": "text/html",
".afl": "video/animaflex",
".ai": "application/postscript",
".aif": "audio/aiff",
".aifc": "audio/aiff",
".aiff": "audio/aiff",
".aim": "application/x-aim",
".aip": "text/x-audiosoft-intra",
".alz": "application/x-alz-compressed",
".ani": "application/x-navi-animation",
".aos": "application/x-nokia-9000-communicator-add-on-software",
".aps": "application/mime",
".apk": "application/vnd.android.package-archive",
".arc": "application/x-arc-compressed",
".arj": "application/arj",
".art": "image/x-jg",
".asf": "video/x-ms-asf",
".asm": "text/x-asm",
".asp": "text/asp",
".asx": "application/x-mplayer2",
".au": "audio/basic",
".avi": "video/x-msvideo",
".avs": "video/avs-video",
".bcpio": "application/x-bcpio",
".bin": "application/mac-binary",
".bmp": "image/bmp",
".boo": "application/book",
".book": "application/book",
".boz": "application/x-bzip2",
".bsh": "application/x-bsh",
".bz2": "application/x-bzip2",
".bz": "application/x-bzip",
".c++": "text/plain",
".c": "text/x-c",
".cab": "application/vnd.ms-cab-compressed",
".cat": "application/vndms-pkiseccat",
".cc": "text/x-c",
".ccad": "application/clariscad",
".cco": "application/x-cocoa",
".cdf": "application/cdf",
".cer": "application/pkix-cert",
".cha": "application/x-chat",
".chat": "application/x-chat",
".chrt": "application/vnd.kde.kchart",
".class": "application/java",
".com": "text/plain",
".conf": "text/plain",
".cpio": "application/x-cpio",
".cpp": "text/x-c",
".cpt": "application/mac-compactpro",
".crl": "application/pkcs-crl",
".crt": "application/pkix-cert",
".crx": "application/x-chrome-extension",
".csh": "text/x-scriptcsh",
".css": "text/css",
".csv": "text/csv",
".cxx": "text/plain",
".dar": "application/x-dar",
".dcr": "application/x-director",
".deb": "application/x-debian-package",
".deepv": "application/x-deepv",
".def": "text/plain",
".der": "application/x-x509-ca-cert",
".dif": "video/x-dv",
".dir": "application/x-director",
".divx": "video/divx",
".dl": "video/dl",
".dmg": "application/x-apple-diskimage",
".doc": "application/msword",
".dot": "application/msword",
".dp": "application/commonground",
".drw": "application/drafting",
".dump": "application/octet-stream",
".dv": "video/x-dv",
".dvi": "application/x-dvi",
".dwf": "drawing/x-dwf=(old)",
".dwg": "application/acad",
".dxf": "application/dxf",
".dxr": "application/x-director",
".el": "text/x-scriptelisp",
".elc": "application/x-bytecodeelisp=(compiled=elisp)",
".eml": "message/rfc822",
".env": "application/x-envoy",
".eps": "application/postscript",
".es": "application/x-esrehber",
".etx": "text/x-setext",
".evy": "application/envoy",
".exe": "application/octet-stream",
".f77": "text/x-fortran",
".f90": "text/x-fortran",
".f": "text/x-fortran",
".fdf": "application/vndfdf",
".fif": "application/fractals",
".fli": "video/fli",
".flo": "image/florian",
".flv": "video/x-flv",
".flx": "text/vndfmiflexstor",
".fmf": "video/x-atomic3d-feature",
".for": "text/x-fortran",
".fpx": "image/vndfpx",
".frl": "application/freeloader",
".funk": "audio/make",
".g3": "image/g3fax",
".g": "text/plain",
".gif": "image/gif",
".gl": "video/gl",
".gsd": "audio/x-gsm",
".gsm": "audio/x-gsm",
".gsp": "application/x-gsp",
".gss": "application/x-gss",
".gtar": "application/x-gtar",
".gz": "application/x-compressed",
".gzip": "application/x-gzip",
".h": "text/x-h",
".hdf": "application/x-hdf",
".help": "application/x-helpfile",
".hgl": "application/vndhp-hpgl",
".hh": "text/x-h",
".hlb": "text/x-script",
".hlp": "application/hlp",
".hpg": "application/vndhp-hpgl",
".hpgl": "application/vndhp-hpgl",
".hqx": "application/binhex",
".hta": "application/hta",
".htc": "text/x-component",
".htm": "text/html",
".html": "text/html",
".htmls": "text/html",
".htt": "text/webviewhtml",
".htx": "text/html",
".ice": "x-conference/x-cooltalk",
".ico": "image/x-icon",
".ics": "text/calendar",
".icz": "text/calendar",
".idc": "text/plain",
".ief": "image/ief",
".iefs": "image/ief",
".iges": "application/iges",
".igs": "application/iges",
".ima": "application/x-ima",
".imap": "application/x-httpd-imap",
".inf": "application/inf",
".ins": "application/x-internett-signup",
".ip": "application/x-ip2",
".isu": "video/x-isvideo",
".it": "audio/it",
".iv": "application/x-inventor",
".ivr": "i-world/i-vrml",
".ivy": "application/x-livescreen",
".jam": "audio/x-jam",
".jav": "text/x-java-source",
".java": "text/x-java-source",
".jcm": "application/x-java-commerce",
".jfif-tbnl": "image/jpeg",
".jfif": "image/jpeg",
".jnlp": "application/x-java-jnlp-file",
".jpe": "image/jpeg",
".jpeg": "image/jpeg",
".jpg": "image/jpeg",
".jps": "image/x-jps",
".js": "application/javascript",
".json": "application/json",
".jut": "image/jutvision",
".kar": "audio/midi",
".karbon": "application/vnd.kde.karbon",
".kfo": "application/vnd.kde.kformula",
".flw": "application/vnd.kde.kivio",
".kml": "application/vnd.google-earth.kml+xml",
".kmz": "application/vnd.google-earth.kmz",
".kon": "application/vnd.kde.kontour",
".kpr": "application/vnd.kde.kpresenter",
".kpt": "application/vnd.kde.kpresenter",
".ksp": "application/vnd.kde.kspread",
".kwd": "application/vnd.kde.kword",
".kwt": "application/vnd.kde.kword",
".ksh": "text/x-scriptksh",
".la": "audio/nspaudio",
".lam": "audio/x-liveaudio",
".latex": "application/x-latex",
".lha": "application/lha",
".lhx": "application/octet-stream",
".list": "text/plain",
".lma": "audio/nspaudio",
".log": "text/plain",
".lsp": "text/x-scriptlisp",
".lst": "text/plain",
".lsx": "text/x-la-asf",
".ltx": "application/x-latex",
".lzh": "application/octet-stream",
".lzx": "application/lzx",
".m1v": "video/mpeg",
".m2a": "audio/mpeg",
".m2v": "video/mpeg",
".m3u": "audio/x-mpegurl",
".m": "text/x-m",
".man": "application/x-troff-man",
".manifest": "text/cache-manifest",
".map": "application/x-navimap",
".mar": "text/plain",
".mbd": "application/mbedlet",
".mc$": "application/x-magic-cap-package-10",
".mcd": "application/mcad",
".mcf": "text/mcf",
".mcp": "application/netmc",
".me": "application/x-troff-me",
".mht": "message/rfc822",
".mhtml": "message/rfc822",
".mid": "application/x-midi",
".midi": "application/x-midi",
".mif": "application/x-frame",
".mime": "message/rfc822",
".mjf": "audio/x-vndaudioexplosionmjuicemediafile",
".mjpg": "video/x-motion-jpeg",
".mm": "application/base64",
".mme": "application/base64",
".mod": "audio/mod",
".moov": "video/quicktime",
".mov": "video/quicktime",
".movie": "video/x-sgi-movie",
".mp2": "audio/mpeg",
".mp3": "audio/mpeg3",
".mp4": "video/mp4",
".mpa": "audio/mpeg",
".mpc": "application/x-project",
".mpe": "video/mpeg",
".mpeg": "video/mpeg",
".mpg": "video/mpeg",
".mpga": "audio/mpeg",
".mpp": "application/vndms-project",
".mpt": "application/x-project",
".mpv": "application/x-project",
".mpx": "application/x-project",
".mrc": "application/marc",
".ms": "application/x-troff-ms",
".mv": "video/x-sgi-movie",
".my": "audio/make",
".mzz": "application/x-vndaudioexplosionmzz",
".nap": "image/naplps",
".naplps": "image/naplps",
".nc": "application/x-netcdf",
".ncm": "application/vndnokiaconfiguration-message",
".nif": "image/x-niff",
".niff": "image/x-niff",
".nix": "application/x-mix-transfer",
".nsc": "application/x-conference",
".nvd": "application/x-navidoc",
".o": "application/octet-stream",
".oda": "application/oda",
".odb": "application/vnd.oasis.opendocument.database",
".odc": "application/vnd.oasis.opendocument.chart",
".odf": "application/vnd.oasis.opendocument.formula",
".odg": "application/vnd.oasis.opendocument.graphics",
".odi": "application/vnd.oasis.opendocument.image",
".odm": "application/vnd.oasis.opendocument.text-master",
".odp": "application/vnd.oasis.opendocument.presentation",
".ods": "application/vnd.oasis.opendocument.spreadsheet",
".odt": "application/vnd.oasis.opendocument.text",
".oga": "audio/ogg",
".ogg": "audio/ogg",
".ogv": "video/ogg",
".omc": "application/x-omc",
".omcd": "application/x-omcdatamaker",
".omcr": "application/x-omcregerator",
".otc": "application/vnd.oasis.opendocument.chart-template",
".otf": "application/vnd.oasis.opendocument.formula-template",
".otg": "application/vnd.oasis.opendocument.graphics-template",
".oth": "application/vnd.oasis.opendocument.text-web",
".oti": "application/vnd.oasis.opendocument.image-template",
".otm": "application/vnd.oasis.opendocument.text-master",
".otp": "application/vnd.oasis.opendocument.presentation-template",
".ots": "application/vnd.oasis.opendocument.spreadsheet-template",
".ott": "application/vnd.oasis.opendocument.text-template",
".p10": "application/pkcs10",
".p12": "application/pkcs-12",
".p7a": "application/x-pkcs7-signature",
".p7c": "application/pkcs7-mime",
".p7m": "application/pkcs7-mime",
".p7r": "application/x-pkcs7-certreqresp",
".p7s": "application/pkcs7-signature",
".p": "text/x-pascal",
".part": "application/pro_eng",
".pas": "text/pascal",
".pbm": "image/x-portable-bitmap",
".pcl": "application/vndhp-pcl",
".pct": "image/x-pict",
".pcx": "image/x-pcx",
".pdb": "chemical/x-pdb",
".pdf": "application/pdf",
".pfunk": "audio/make",
".pgm": "image/x-portable-graymap",
".pic": "image/pict",
".pict": "image/pict",
".pkg": "application/x-newton-compatible-pkg",
".pko": "application/vndms-pkipko",
".pl": "text/x-scriptperl",
".plx": "application/x-pixclscript",
".pm4": "application/x-pagemaker",
".pm5": "application/x-pagemaker",
".pm": "text/x-scriptperl-module",
".png": "image/png",
".pnm": "application/x-portable-anymap",
".pot": "application/mspowerpoint",
".pov": "model/x-pov",
".ppa": "application/vndms-powerpoint",
".ppm": "image/x-portable-pixmap",
".pps": "application/mspowerpoint",
".ppt": "application/mspowerpoint",
".ppz": "application/mspowerpoint",
".pre": "application/x-freelance",
".prt": "application/pro_eng",
".ps": "application/postscript",
".psd": "application/octet-stream",
".pvu": "paleovu/x-pv",
".pwz": "application/vndms-powerpoint",
".py": "text/x-scriptphyton",
".pyc": "application/x-bytecodepython",
".qcp": "audio/vndqcelp",
".qd3": "x-world/x-3dmf",
".qd3d": "x-world/x-3dmf",
".qif": "image/x-quicktime",
".qt": "video/quicktime",
".qtc": "video/x-qtc",
".qti": "image/x-quicktime",
".qtif": "image/x-quicktime",
".ra": "audio/x-pn-realaudio",
".ram": "audio/x-pn-realaudio",
".rar": "application/x-rar-compressed",
".ras": "application/x-cmu-raster",
".rast": "image/cmu-raster",
".rexx": "text/x-scriptrexx",
".rf": "image/vndrn-realflash",
".rgb": "image/x-rgb",
".rm": "application/vndrn-realmedia",
".rmi": "audio/mid",
".rmm": "audio/x-pn-realaudio",
".rmp": "audio/x-pn-realaudio",
".rng": "application/ringing-tones",
".rnx": "application/vndrn-realplayer",
".roff": "application/x-troff",
".rp": "image/vndrn-realpix",
".rpm": "audio/x-pn-realaudio-plugin",
".rt": "text/vndrn-realtext",
".rtf": "text/richtext",
".rtx": "text/richtext",
".rv": "video/vndrn-realvideo",
".s": "text/x-asm",
".s3m": "audio/s3m",
".s7z": "application/x-7z-compressed",
".saveme": "application/octet-stream",
".sbk": "application/x-tbook",
".scm": "text/x-scriptscheme",
".sdml": "text/plain",
".sdp": "application/sdp",
".sdr": "application/sounder",
".sea": "application/sea",
".set": "application/set",
".sgm": "text/x-sgml",
".sgml": "text/x-sgml",
".sh": "text/x-scriptsh",
".shar": "application/x-bsh",
".shtml": "text/x-server-parsed-html",
".sid": "audio/x-psid",
".skd": "application/x-koan",
".skm": "application/x-koan",
".skp": "application/x-koan",
".skt": "application/x-koan",
".sit": "application/x-stuffit",
".sitx": "application/x-stuffitx",
".sl": "application/x-seelogo",
".smi": "application/smil",
".smil": "application/smil",
".snd": "audio/basic",
".sol": "application/solids",
".spc": "text/x-speech",
".spl": "application/futuresplash",
".spr": "application/x-sprite",
".sprite": "application/x-sprite",
".spx": "audio/ogg",
".src": "application/x-wais-source",
".ssi": "text/x-server-parsed-html",
".ssm": "application/streamingmedia",
".sst": "application/vndms-pkicertstore",
".step": "application/step",
".stl": "application/sla",
".stp": "application/step",
".sv4cpio": "application/x-sv4cpio",
".sv4crc": "application/x-sv4crc",
".svf": "image/vnddwg",
".svg": "image/svg+xml",
".svr": "application/x-world",
".swf": "application/x-shockwave-flash",
".t": "application/x-troff",
".talk": "text/x-speech",
".tar": "application/x-tar",
".tbk": "application/toolbook",
".tcl": "text/x-scripttcl",
".tcsh": "text/x-scripttcsh",
".tex": "application/x-tex",
".texi": "application/x-texinfo",
".texinfo": "application/x-texinfo",
".text": "text/plain",
".tgz": "application/gnutar",
".tif": "image/tiff",
".tiff": "image/tiff",
".tr": "application/x-troff",
".tsi": "audio/tsp-audio",
".tsp": "application/dsptype",
".tsv": "text/tab-separated-values",
".turbot": "image/florian",
".txt": "text/plain",
".uil": "text/x-uil",
".uni": "text/uri-list",
".unis": "text/uri-list",
".unv": "application/i-deas",
".uri": "text/uri-list",
".uris": "text/uri-list",
".ustar": "application/x-ustar",
".uu": "text/x-uuencode",
".uue": "text/x-uuencode",
".vcd": "application/x-cdlink",
".vcf": "text/x-vcard",
".vcard": "text/x-vcard",
".vcs": "text/x-vcalendar",
".vda": "application/vda",
".vdo": "video/vdo",
".vew": "application/groupwise",
".viv": "video/vivo",
".vivo": "video/vivo",
".vmd": "application/vocaltec-media-desc",
".vmf": "application/vocaltec-media-file",
".voc": "audio/voc",
".vos": "video/vosaic",
".vox": "audio/voxware",
".vqe": "audio/x-twinvq-plugin",
".vqf": "audio/x-twinvq",
".vql": "audio/x-twinvq-plugin",
".vrml": "application/x-vrml",
".vrt": "x-world/x-vrt",
".vsd": "application/x-visio",
".vst": "application/x-visio",
".vsw": "application/x-visio",
".w60": "application/wordperfect60",
".w61": "application/wordperfect61",
".w6w": "application/msword",
".wav": "audio/wav",
".wb1": "application/x-qpro",
".wbmp": "image/vnd.wap.wbmp",
".web": "application/vndxara",
".wiz": "application/msword",
".wk1": "application/x-123",
".wmf": "windows/metafile",
".wml": "text/vnd.wap.wml",
".wmlc": "application/vnd.wap.wmlc",
".wmls": "text/vnd.wap.wmlscript",
".wmlsc": "application/vnd.wap.wmlscriptc",
".word": "application/msword",
".wp5": "application/wordperfect",
".wp6": "application/wordperfect",
".wp": "application/wordperfect",
".wpd": "application/wordperfect",
".wq1": "application/x-lotus",
".wri": "application/mswrite",
".wrl": "application/x-world",
".wrz": "model/vrml",
".wsc": "text/scriplet",
".wsrc": "application/x-wais-source",
".wtk": "application/x-wintalk",
".x-png": "image/png",
".xbm": "image/x-xbitmap",
".xdr": "video/x-amt-demorun",
".xgz": "xgl/drawing",
".xif": "image/vndxiff",
".xl": "application/excel",
".xla": "application/excel",
".xlb": "application/excel",
".xlc": "application/excel",
".xld": "application/excel",
".xlk": "application/excel",
".xll": "application/excel",
".xlm": "application/excel",
".xls": "application/excel",
".xlt": "application/excel",
".xlv": "application/excel",
".xlw": "application/excel",
".xm": "audio/xm",
".xml": "text/xml",
".xmz": "xgl/movie",
".xpix": "application/x-vndls-xpix",
".xpm": "image/x-xpixmap",
".xsr": "video/x-amt-showrun",
".xwd": "image/x-xwd",
".xyz": "chemical/x-pdb",
".z": "application/x-compress",
".zip": "application/zip",
".zoo": "application/octet-stream",
".zsh": "text/x-scriptzsh",
".docx": "application/vnd.openxmlformats-officedocument.wordprocessingml.document",
".docm": "application/vnd.ms-word.document.macroEnabled.12",
".dotx": "application/vnd.openxmlformats-officedocument.wordprocessingml.template",
".dotm": "application/vnd.ms-word.template.macroEnabled.12",
".xlsx": "application/vnd.openxmlformats-officedocument.spreadsheetml.sheet",
".xlsm": "application/vnd.ms-excel.sheet.macroEnabled.12",
".xltx": "application/vnd.openxmlformats-officedocument.spreadsheetml.template",
".xltm": "application/vnd.ms-excel.template.macroEnabled.12",
".xlsb": "application/vnd.ms-excel.sheet.binary.macroEnabled.12",
".xlam": "application/vnd.ms-excel.addin.macroEnabled.12",
".pptx": "application/vnd.openxmlformats-officedocument.presentationml.presentation",
".pptm": "application/vnd.ms-powerpoint.presentation.macroEnabled.12",
".ppsx": "application/vnd.openxmlformats-officedocument.presentationml.slideshow",
".ppsm": "application/vnd.ms-powerpoint.slideshow.macroEnabled.12",
".potx": "application/vnd.openxmlformats-officedocument.presentationml.template",
".potm": "application/vnd.ms-powerpoint.template.macroEnabled.12",
".ppam": "application/vnd.ms-powerpoint.addin.macroEnabled.12",
".sldx": "application/vnd.openxmlformats-officedocument.presentationml.slide",
".sldm": "application/vnd.ms-powerpoint.slide.macroEnabled.12",
".thmx": "application/vnd.ms-officetheme",
".onetoc": "application/onenote",
".onetoc2": "application/onenote",
".onetmp": "application/onenote",
".onepkg": "application/onenote",
".xpi": "application/x-xpinstall",
}
func init() {
for ext, typ := range types {
// skip errors
mime.AddExtensionType(ext, typ)
}
}
// typeByExtension returns the MIME type associated with the file extension ext.
// The extension ext should begin with a leading dot, as in ".html".
// When ext has no associated type, typeByExtension returns "".
//
// Extensions are looked up first case-sensitively, then case-insensitively.
//
// The built-in table is small but on unix it is augmented by the local
// system's mime.types file(s) if available under one or more of these
// names:
//
// /etc/mime.types
// /etc/apache2/mime.types
// /etc/apache/mime.types
//
// On Windows, MIME types are extracted from the registry.
//
// Text types have the charset parameter set to "utf-8" by default.
func TypeByExtension(fullfilename string) string {
ext := filepath.Ext(fullfilename)
typ := mime.TypeByExtension(ext)
// mime.TypeByExtension returns as text/plain; | charset=utf-8 the static .js (not always)
if ext == ".js" && (typ == "text/plain" || typ == "text/plain; charset=utf-8") {
if ext == ".js" {
typ = "application/javascript"
}
}
return typ
}
Espero que te haya ayudado a ti y a otros usuarios, ¡no dudes en volver a publicar si tienes más preguntas!
init()
es una cosa por paquete, creo ... Por lo tanto, ¿significa que si diferentes archivos tienen los suyosinits
, todas las entradas siempre se ejecutan justo antes de que se ejecute main ()? ¿También puede aclararme una cosa, por qué tendría un init () sin main y cómo funciona? ¿Significa que init () es lo último que se ejecutó antes de importar el paquete? De lo contrario, si no se importa y no hay main, el programa nunca se ejecutará ... ¿verdad? (a menos que sea un archivo de prueba, supongo ...)