generateMimeTypes.js

var fs = require('fs');

var text = fs.readFileSync('/usr/local/etc/nginx/mime.types').toString('utf8');

var lines = text
.replace(/[\s\n]*types\s*{/, '')
.replace(/}[\s\n]*/, '')
.replace(/\n\s+/g, '\n')
.split('\n')
.filter(function(l) { return /^[^\s]/.test(l) })
.map(function(l) {
  var m = l.match(/^([^\s]+)\s+([^;]+);/);
  return [m[1], m[2].split(' ')];
});

var map = {};

lines.forEach(function(l) {
  l[1].forEach(function(ext) {
    map[ext] = l[0];
  })
});

console.info(JSON.stringify(map, null, 2));

MimeType.swift

internal let DEFAULT_MIME_TYPE = "application/octet-stream"

internal let mimeTypes = [
    "html": "text/html",
    "htm": "text/html",
    "shtml": "text/html",
    "css": "text/css",
    "xml": "text/xml",
    "gif": "image/gif",
    "jpeg": "image/jpeg",
    "jpg": "image/jpeg",
    "js": "application/javascript",
    "atom": "application/atom+xml",
    "rss": "application/rss+xml",
    "mml": "text/mathml",
    "txt": "text/plain",
    "jad": "text/vnd.sun.j2me.app-descriptor",
    "wml": "text/vnd.wap.wml",
    "htc": "text/x-component",
    "png": "image/png",
    "tif": "image/tiff",
    "tiff": "image/tiff",
    "wbmp": "image/vnd.wap.wbmp",
    "ico": "image/x-icon",
    "jng": "image/x-jng",
    "bmp": "image/x-ms-bmp",
    "svg": "image/svg+xml",
    "svgz": "image/svg+xml",
    "webp": "image/webp",
    "woff": "application/font-woff",
    "jar": "application/java-archive",
    "war": "application/java-archive",
    "ear": "application/java-archive",
    "json": "application/json",
    "hqx": "application/mac-binhex40",
    "doc": "application/msword",
    "pdf": "application/pdf",
    "ps": "application/postscript",
    "eps": "application/postscript",
    "ai": "application/postscript",
    "rtf": "application/rtf",
    "m3u8": "application/vnd.apple.mpegurl",
    "xls": "application/vnd.ms-excel",
    "eot": "application/vnd.ms-fontobject",
    "ppt": "application/vnd.ms-powerpoint",
    "wmlc": "application/vnd.wap.wmlc",
    "kml": "application/vnd.google-earth.kml+xml",
    "kmz": "application/vnd.google-earth.kmz",
    "7z": "application/x-7z-compressed",
    "cco": "application/x-cocoa",
    "jardiff": "application/x-java-archive-diff",
    "jnlp": "application/x-java-jnlp-file",
    "run": "application/x-makeself",
    "pl": "application/x-perl",
    "pm": "application/x-perl",
    "prc": "application/x-pilot",
    "pdb": "application/x-pilot",
    "rar": "application/x-rar-compressed",
    "rpm": "application/x-redhat-package-manager",
    "sea": "application/x-sea",
    "swf": "application/x-shockwave-flash",
    "sit": "application/x-stuffit",
    "tcl": "application/x-tcl",
    "tk": "application/x-tcl",
    "der": "application/x-x509-ca-cert",
    "pem": "application/x-x509-ca-cert",
    "crt": "application/x-x509-ca-cert",
    "xpi": "application/x-xpinstall",
    "xhtml": "application/xhtml+xml",
    "xspf": "application/xspf+xml",
    "zip": "application/zip",
    "bin": "application/octet-stream",
    "exe": "application/octet-stream",
    "dll": "application/octet-stream",
    "deb": "application/octet-stream",
    "dmg": "application/octet-stream",
    "iso": "application/octet-stream",
    "img": "application/octet-stream",
    "msi": "application/octet-stream",
    "msp": "application/octet-stream",
    "msm": "application/octet-stream",
    "docx": "application/vnd.openxmlformats-officedocument.wordprocessingml.document",
    "xlsx": "application/vnd.openxmlformats-officedocument.spreadsheetml.sheet",
    "pptx": "application/vnd.openxmlformats-officedocument.presentationml.presentation",
    "mid": "audio/midi",
    "midi": "audio/midi",
    "kar": "audio/midi",
    "mp3": "audio/mpeg",
    "ogg": "audio/ogg",
    "m4a": "audio/x-m4a",
    "ra": "audio/x-realaudio",
    "3gpp": "video/3gpp",
    "3gp": "video/3gpp",
    "ts": "video/mp2t",
    "mp4": "video/mp4",
    "mpeg": "video/mpeg",
    "mpg": "video/mpeg",
    "mov": "video/quicktime",
    "webm": "video/webm",
    "flv": "video/x-flv",
    "m4v": "video/x-m4v",
    "mng": "video/x-mng",
    "asx": "video/x-ms-asf",
    "asf": "video/x-ms-asf",
    "wmv": "video/x-ms-wmv",
    "avi": "video/x-msvideo"
]

internal func MimeType(ext: String?) -> String {
    if ext != nil && mimeTypes.contains({ $0.0 == ext!.lowercaseString }) {
        return mimeTypes[ext!.lowercaseString]!
    }
    return DEFAULT_MIME_TYPE
}

extension NSURL {
    public func mimeType() -> String {
        return MimeType(self.pathExtension)
    }
}


extension NSString {
    public func mimeType() -> String {
        return MimeType(self.pathExtension)
    }
}

extension String {
    public func mimeType() -> String {
        return (self as NSString).mimeType()
    }
}

mimeTypes.json

{
  "html": "text/html",
  "htm": "text/html",
  "shtml": "text/html",
  "css": "text/css",
  "xml": "text/xml",
  "gif": "image/gif",
  "jpeg": "image/jpeg",
  "jpg": "image/jpeg",
  "js": "application/javascript",
  "atom": "application/atom+xml",
  "rss": "application/rss+xml",
  "mml": "text/mathml",
  "txt": "text/plain",
  "jad": "text/vnd.sun.j2me.app-descriptor",
  "wml": "text/vnd.wap.wml",
  "htc": "text/x-component",
  "png": "image/png",
  "tif": "image/tiff",
  "tiff": "image/tiff",
  "wbmp": "image/vnd.wap.wbmp",
  "ico": "image/x-icon",
  "jng": "image/x-jng",
  "bmp": "image/x-ms-bmp",
  "svg": "image/svg+xml",
  "svgz": "image/svg+xml",
  "webp": "image/webp",
  "woff": "application/font-woff",
  "jar": "application/java-archive",
  "war": "application/java-archive",
  "ear": "application/java-archive",
  "json": "application/json",
  "hqx": "application/mac-binhex40",
  "doc": "application/msword",
  "pdf": "application/pdf",
  "ps": "application/postscript",
  "eps": "application/postscript",
  "ai": "application/postscript",
  "rtf": "application/rtf",
  "m3u8": "application/vnd.apple.mpegurl",
  "xls": "application/vnd.ms-excel",
  "eot": "application/vnd.ms-fontobject",
  "ppt": "application/vnd.ms-powerpoint",
  "wmlc": "application/vnd.wap.wmlc",
  "kml": "application/vnd.google-earth.kml+xml",
  "kmz": "application/vnd.google-earth.kmz",
  "7z": "application/x-7z-compressed",
  "cco": "application/x-cocoa",
  "jardiff": "application/x-java-archive-diff",
  "jnlp": "application/x-java-jnlp-file",
  "run": "application/x-makeself",
  "pl": "application/x-perl",
  "pm": "application/x-perl",
  "prc": "application/x-pilot",
  "pdb": "application/x-pilot",
  "rar": "application/x-rar-compressed",
  "rpm": "application/x-redhat-package-manager",
  "sea": "application/x-sea",
  "swf": "application/x-shockwave-flash",
  "sit": "application/x-stuffit",
  "tcl": "application/x-tcl",
  "tk": "application/x-tcl",
  "der": "application/x-x509-ca-cert",
  "pem": "application/x-x509-ca-cert",
  "crt": "application/x-x509-ca-cert",
  "xpi": "application/x-xpinstall",
  "xhtml": "application/xhtml+xml",
  "xspf": "application/xspf+xml",
  "zip": "application/zip",
  "bin": "application/octet-stream",
  "exe": "application/octet-stream",
  "dll": "application/octet-stream",
  "deb": "application/octet-stream",
  "dmg": "application/octet-stream",
  "iso": "application/octet-stream",
  "img": "application/octet-stream",
  "msi": "application/octet-stream",
  "msp": "application/octet-stream",
  "msm": "application/octet-stream",
  "docx": "application/vnd.openxmlformats-officedocument.wordprocessingml.document",
  "xlsx": "application/vnd.openxmlformats-officedocument.spreadsheetml.sheet",
  "pptx": "application/vnd.openxmlformats-officedocument.presentationml.presentation",
  "mid": "audio/midi",
  "midi": "audio/midi",
  "kar": "audio/midi",
  "mp3": "audio/mpeg",
  "ogg": "audio/ogg",
  "m4a": "audio/x-m4a",
  "ra": "audio/x-realaudio",
  "3gpp": "video/3gpp",
  "3gp": "video/3gpp",
  "ts": "video/mp2t",
  "mp4": "video/mp4",
  "mpeg": "video/mpeg",
  "mpg": "video/mpeg",
  "mov": "video/quicktime",
  "webm": "video/webm",
  "flv": "video/x-flv",
  "m4v": "video/x-m4v",
  "mng": "video/x-mng",
  "asx": "video/x-ms-asf",
  "asf": "video/x-ms-asf",
  "wmv": "video/x-ms-wmv",
  "avi": "video/x-msvideo"
}

Hey, I've made an optimization for Swift where it uses optional in a bit cleaner way. You can check it out on my fork, or just replace it with:

internal func MimeType(ext: String?) -> String {
    if let ext = ext?.lowercased(), let mimeType = mimeTypes[ext] {
        return mimeType
    }else{
        return DEFAULT_MIME_TYPE
    }
}