Scala 阴影/删除字符串插值器

我使用两个库来定义字符串插值器（为了清晰起见，简化了代码）：

:

:

我想同时使用它们，即来自Http4s的

uri

插值器和来自ip4s的各种插值器。问题在于以下代码：

import com.comcast.ip4s._
import org.http4s.syntax.literals._

class Foo(cidr: Cidr[Ipv4Address] = ipv4"192.168.1.1" / 24)

无法使用以下命令编译：

[error] Note that implicit conversions are not applicable because they are ambiguous:
[error]  both method IpLiteralSyntax in package ip4s of type (sc: StringContext): com.comcast.ip4s.package.IpLiteralSyntax
[error]  and method http4sLiteralsSyntax in trait LiteralsSyntax of type (sc: StringContext): org.http4s.syntax.LiteralsOps
[error]  are possible conversion functions from StringContext to ?{def ipv4: ?}
[error]   class Foo(cidr: Cidr[Ipv4Address] = ipv4"192.168.1.1" / 24)

---

是否仍有从隐式作用域中隐藏/删除字符串插值器的方法？

您的问题显然是，

ipv4

和

ipv6

的插值器存在冲突，编译器不知道使用哪一个

冲突隐式ITS问题可以通过赋予其中一个隐式ITS更高的优先级来解决。这可以通过使用推杆来完成

来自

http4s

的隐式可以通过trait

AllSyntax

纳入范围：

import com.comcast.ip4s._
import org.http4s.Uri
import org.http4s.syntax.AllSyntax

case class Foo(cidr: Cidr[Ipv4Address] = ipv4"192.168.1.1" / 24)

class MyApp extends AllSyntax {

  val testUri: Uri = uri"http://test.pl" //we can still use uri interpolator from http4s

}

但这仍然无法编译：

import org.http4s.Uri
import org.http4s.syntax.AllSyntax
import com.comcast.ip4s._

class MyApp extends AllSyntax {

  val testUri: Uri = uri"http://test.pl"
  val ip = ipv4"192.168.1.1" / 24 //compile error

}

不幸的是，

ip4s

并没有提供任何特性来将其引入范围，因此我们可以对其进行优先级排序

您可以创建另一个对象，在其中复制包对象

com.comcast.ip4s

的内部内容，然后扩展所有语法：

import org.http4s.Uri
import org.http4s.syntax.AllSyntax
import com.comcast.ip4s._
import scala.language.experimental.macros

object MySyntax extends AllSyntax {

  //copied from com.comcast.ip4s
  final implicit class IpLiteralSyntax(val sc: StringContext) extends AnyVal {
    def ip(args: Any*): IpAddress = macro LiteralSyntaxMacros.ipInterpolator
    def ipv4(args: Any*): Ipv4Address =
    macro LiteralSyntaxMacros.ipv4Interpolator
    def ipv6(args: Any*): Ipv6Address =
    macro LiteralSyntaxMacros.ipv6Interpolator
    (...)
  }

}

然后你可以这样使用它：

class MyApp extends App {

  import MySyntax._

  val testUri: Uri = uri"http://test.pl"
  val ip = ipv4"192.168.1.1" / 24 //interpolator from com.comcast.ip4s has higher priority

}

---

这将阻止我使用ip4s的ipv4插值器。我希望有一个我不知道的劈刀技巧。也许在多蒂有。谢谢

import org.http4s.Uri
import org.http4s.syntax.AllSyntax
import com.comcast.ip4s._
import scala.language.experimental.macros

object MySyntax extends AllSyntax {

  //copied from com.comcast.ip4s
  final implicit class IpLiteralSyntax(val sc: StringContext) extends AnyVal {
    def ip(args: Any*): IpAddress = macro LiteralSyntaxMacros.ipInterpolator
    def ipv4(args: Any*): Ipv4Address =
    macro LiteralSyntaxMacros.ipv4Interpolator
    def ipv6(args: Any*): Ipv6Address =
    macro LiteralSyntaxMacros.ipv6Interpolator
    (...)
  }

}

class MyApp extends App {

  import MySyntax._

  val testUri: Uri = uri"http://test.pl"
  val ip = ipv4"192.168.1.1" / 24 //interpolator from com.comcast.ip4s has higher priority

}