一次性资源模式 [英] Disposable Resource Pattern

问题描述

Scala 库中是否有任何标准化的内容来支持一次性资源模式?

Is there anything standardized within the Scala library to support the disposable resource pattern?

我的意思是类似于 C# 和 .NET 支持的内容，仅举一个.

I mean something similar to that supported by C# and .NET just to mention one.

例如，官方 Scala 库是否提供了这样的东西:

For example does official Scala library provide something like this:

trait Disposable { def dispose() }

class Resource extends Disposable

using (new Resource) { r =>

}

注意:我知道这篇文章«Scala finally 块关闭/刷新资源» 但它似乎没有集成在标准库中

Note: I'm aware of this article «Scala finally block closing/flushing resource» but it seems not integrated within the standard lib

推荐答案

从 Scala 2.13 开始，标准库提供了专用的资源管理实用程序:使用.

Starting Scala 2.13, the standard library provides a dedicated resource management utility: Using.

您只需要使用 Releasable 特性:

You will just have to provide an implicit definition of how to release the resource, using the Releasable trait:

import scala.util.Using
import scala.util.Using.Releasable

case class Resource(field: String)

implicit val releasable: Releasable[Resource] = resource => println(s"closing $resource")

Using(Resource("hello world")) { resource => resource.field.toInt }
// closing Resource(hello world)
// res0: scala.util.Try[Int] = Failure(java.lang.NumberFormatException: For input string: "hello world")

请注意，为了清楚起见，您可以将隐式可释放对象放在 Resource 的伴随对象中.

Note that you can place the implicit releasable in the companion object of Resource for clarity.

请注意，您也可以使用 Java 的 AutoCloseable 而不是 Using.Releasable，因此任何实现 AutoCloseable 的 Java 或 Scala 对象(例如 scala.io.Source 或 java.io.PrintWriter) 可以直接与 Using 一起使用:

Note that you can also use Java's AutoCloseable instead of Using.Releasable and thus any Java or Scala object implementing AutoCloseable (such as scala.io.Source or java.io.PrintWriter) can directly be used with Using:

import scala.util.Using

case class Resource(field: String) extends AutoCloseable {
  def close(): Unit = println(s"closing $this")
}

Using(Resource("hello world")) { resource => resource.field.toInt }
// closing Resource(hello world)
// res0: scala.util.Try[Int] = Failure(java.lang.NumberFormatException: For input string: "hello world")

这篇关于一次性资源模式的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！