针对 URL 的 Scala 模式匹配
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Scala pattern matching against URLs
提问by Eric Hauser
Is there a Scala library/example that will parse a URL/URI into a case class structure for pattern matching?
是否有 Scala 库/示例可以将 URL/URI 解析为案例类结构以进行模式匹配？
回答by Alex Cruise
Here's an extractor that will get some parts out of a URL for you:
这是一个提取器，可以为您从 URL 中提取某些部分：
object UrlyBurd {
def unapply(in: java.net.URL) = Some((
in.getProtocol,
in.getHost,
in.getPort,
in.getPath
))
}
val u = new java.net.URL("http://www.google.com/")
u match {
case UrlyBurd(protocol, host, port, path) =>
protocol +
"://" + host +
(if (port == -1) "" else ":" + port) +
path
}
回答by Philippe
I would suggest to use the facility provided by extractors for regular expressions.
For instance:
例如：
val URL = """(http|ftp)://(.*)\.([a-z]+)""".r
def splitURL(url : String) = url match {
case URL(protocol, domain, tld) => println((protocol, domain, tld))
}
splitURL("http://www.google.com") // prints (http,www.google,com)
Some explanations:
一些解释：
- The
.rmethod on strings (actually, onStringLikes) turns them into an instance ofRegex. Regexes define anunapplySeqmethod, which allows them to be used as extractorsin pattern-matching (note that you have to give them a name that starts with a capital letter for this to work).- The values that are going to be passed into the binders you use in the pattern are defined by the groups
(...)in the regular expression.
.r字符串上的方法（实际上是StringLikes上的）将它们变成 的实例Regex。Regexes 定义了一个unapplySeq方法，允许它们在模式匹配中用作提取器（请注意，您必须给它们一个以大写字母开头的名称才能工作）。- 将要传递到您在模式中使用的活页夹中的值由
(...)正则表达式中的组定义。
回答by JaimeJorge
You can use java's URLwhich can parse an URL for its different components and is completely Scala compatible.
您可以使用java 的 URL，它可以解析不同组件的 URL，并且完全兼容 Scala。
回答by theon
The following library can help you parse URIs into an instance of a case class. (Disclaimer: it is my own library) https://github.com/theon/scala-uri
以下库可以帮助您将 URI 解析为案例类的实例。（免责声明：这是我自己的图书馆） https://github.com/theon/scala-uri
You parse like so:
你这样解析：
import com.github.theon.uri.Uri._
val uri:Uri = "http://example.com?one=1&two=2"
It provides a DSL for building URLs with query strings:
它提供了一个 DSL，用于使用查询字符串构建 URL：
val uri = "http://example.com" ? ("one" -> 1) & ("two" -> 2)
