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使用正则表达式的 Scala 捕获组

发布于 2024-09-06 00:10:27 字数 499 浏览 8 评论 0 原文

假设我有以下代码：

val string = "one493two483three"
val pattern = """two(\d+)three""".r
pattern.findAllIn(string).foreach(println)

我期望 findAllIn 仅返回 483，但它返回了 two483third。我知道我可以使用 unapply 来仅提取该部分，但我必须为整个字符串提供一个模式，例如：

 val pattern = """one.*two(\d+)three""".r
 val pattern(aMatch) = string
 println(aMatch) // prints 483

是否有另一种方法可以实现此目的，而不使用 < 中的类code>java.util 直接，而不使用 unapp？

原文

Let's say I have this code:

val string = "one493two483three"
val pattern = """two(\d+)three""".r
pattern.findAllIn(string).foreach(println)

I expected findAllIn to only return 483, but instead, it returned two483three. I know I could use unapply to extract only that part, but I'd have to have a pattern for the entire string, something like:

 val pattern = """one.*two(\d+)three""".r
 val pattern(aMatch) = string
 println(aMatch) // prints 483

Is there another way of achieving this, without using the classes from java.util directly, and without using unapply?

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￠好甜 2024-09-13 00:10:27

以下是如何访问每场比赛的 group(1) 的示例：

val string = "one493two483three"
val pattern = """two(\d+)three""".r
pattern.findAllIn(string).matchData foreach {
   m => println(m.group(1))
}

这会打印 "483" (如 ideone.com 上所见）。

环视选项

根据模式的复杂性，您还可以使用环视来仅匹配您想要的部分。它看起来像这样：

val string = "one493two483three"
val pattern = """(?<=two)\d+(?=three)""".r
pattern.findAllIn(string).foreach(println)

上面还打印 "483" （如 ideone.com 上所示）。

参考文献

regular-expressions.info/Lookarounds

Here's an example of how you can access group(1) of each match:

val string = "one493two483three"
val pattern = """two(\d+)three""".r
pattern.findAllIn(string).matchData foreach {
   m => println(m.group(1))
}

This prints "483" (as seen on ideone.com).

The lookaround option

Depending on the complexity of the pattern, you can also use lookarounds to only match the portion you want. It'll look something like this:

val string = "one493two483three"
val pattern = """(?<=two)\d+(?=three)""".r
pattern.findAllIn(string).foreach(println)

The above also prints "483" (as seen on ideone.com).

References

regular-expressions.info/Lookarounds

回复收藏 0 原文

一人独醉 2024-09-13 00:10:27

val string = "one493two483three"
val pattern = """.*two(\d+)three.*""".r

string match {
  case pattern(a483) => println(a483) //matched group(1) assigned to variable a483
  case _ => // no match
}

val string = "one493two483three"
val pattern = """.*two(\d+)three.*""".r

string match {
  case pattern(a483) => println(a483) //matched group(1) assigned to variable a483
  case _ => // no match
}

回复收藏 0 原文

爱格式化 2024-09-13 00:10:27

从 Scala 2.13 开始，作为正则表达式解决方案的替代方案，还可以通过取消应用字符串插值器：

"one493two483three" match { case s"${x}two${y}three" => y }
// String = "483"

甚至：

val s"${x}two${y}three" = "one493two483three"
// x: String = one493
// y: String = 483

如果您期望不匹配的输入，您可以添加默认模式保护：

"one493deux483three" match {
  case s"${x}two${y}three" => y
  case _                   => "no match"
}
// String = "no match"

Starting Scala 2.13, as an alternative to regex solutions, it's also possible to pattern match a String by unapplying a string interpolator:

"one493two483three" match { case s"${x}two${y}three" => y }
// String = "483"

Or even:

val s"${x}two${y}three" = "one493two483three"
// x: String = one493
// y: String = 483

If you expect non matching input, you can add a default pattern guard:

"one493deux483three" match {
  case s"${x}two${y}three" => y
  case _                   => "no match"
}
// String = "no match"

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寄风 2024-09-13 00:10:27

您想要查看group(1)，当前正在查看group(0)，它是“整个匹配的字符串”。

请参阅此正则表达式教程。

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谁的新欢旧爱 2024-09-13 00:10:27

def extractFileNameFromHttpFilePathExpression(expr: String) = {
//define regex
val regex = "http4.*\\/(\\w+.(xlsx|xls|zip))$".r
// findFirstMatchIn/findAllMatchIn returns Option[Match] and Match has methods to access capture groups.
regex.findFirstMatchIn(expr) match {
  case Some(i) => i.group(1)
  case None => "regex_error"
}
}
extractFileNameFromHttpFilePathExpression(
    "http4://testing.bbmkl.com/document/sth1234.zip")

def extractFileNameFromHttpFilePathExpression(expr: String) = {
//define regex
val regex = "http4.*\\/(\\w+.(xlsx|xls|zip))$".r
// findFirstMatchIn/findAllMatchIn returns Option[Match] and Match has methods to access capture groups.
regex.findFirstMatchIn(expr) match {
  case Some(i) => i.group(1)
  case None => "regex_error"
}
}
extractFileNameFromHttpFilePathExpression(
    "http4://testing.bbmkl.com/document/sth1234.zip")

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