Slick 3.1.1 未找到类型 'column'

Question

我正在使用 Scala Slick beginner guide 尝试创建一个简单的模式，但在导入文档开头的内容时我似乎找不到 'column' 类型。

import slick.driver.H2Driver.api._
import scala.concurrent.ExecutionContext.Implicits.global
/**
  * Created by chris on 9/7/16.
  */
class BlockHeaderTable(tag: Tag) extends Table[BlockHeader](tag,"block_headers")  {

  def version: column[UInt32]

  def previousBlockHash: column[DoubleSha256Digest]

  def merkleRootHash: column[DoubleSha256Digest]

  def time: column[UInt32]

  def nBits: column[UInt32]

  def nonce: column[UInt32]


}

这是我得到的错误：

chris@chris-870Z5E-880Z5E-680Z5E:~/dev/bitcoins-spv-node$ sbt compile [info] Loading project definition from /home/chris/dev/bitcoins-spv-node/project [info] Set current project to bitcoins-spv-node (in build file:/home/chris/dev/bitcoins-spv-node/) [info] Compiling 1 Scala source to /home/chris/dev/bitcoins-spv-node/target/scala-2.11/classes... [error] /home/chris/dev/bitcoins-spv-node/src/main/scala/org/bitcoins/spvnode/models/BlockHeaderTable.scala:14: not found: type column [error] def version: column[UInt32] [error]
^ [error] /home/chris/dev/bitcoins-spv-node/src/main/scala/org/bitcoins/spvnode/models/BlockHeaderTable.scala:16: not found: type column [error] def previousBlockHash: column[DoubleSha256Digest] [error] ^ [error] /home/chris/dev/bitcoins-spv-node/src/main/scala/org/bitcoins/spvnode/models/BlockHeaderTable.scala:18: not found: type column [error] def merkleRootHash: column[DoubleSha256Digest] [error] ^ [error] /home/chris/dev/bitcoins-spv-node/src/main/scala/org/bitcoins/spvnode/models/BlockHeaderTable.scala:20: not found: type column [error] def time: column[UInt32] [error]
^ [error] /home/chris/dev/bitcoins-spv-node/src/main/scala/org/bitcoins/spvnode/models/BlockHeaderTable.scala:22: not found: type column [error] def nBits: column[UInt32] [error]
^ [error] /home/chris/dev/bitcoins-spv-node/src/main/scala/org/bitcoins/spvnode/models/BlockHeaderTable.scala:24: not found: type column [error] def nonce: column[UInt32] [error]
^ [error] 6 errors found [error] (compile:compileIncremental) Compilation failed

Answer 1

Slick 无法理解标准 JDBC 类型以外的自定义类型，例如 Timestamp、Long、String、Char、Boolean 等。为了使用自定义类型，您必须提供自定义类型的 Slick 映射jdbc 种。

为 UInt32 和 DoubleSha256Digest

提供灵活的映射

例如

DateTime是slick不理解的自定义类型，但是slick理解java.sql.Timestamp。我们提供了一个slick映射。这样 slick 就可以理解如何处理 DateTime

implicit def jodaTimeMapping: BaseColumnType[DateTime] = MappedColumnType.base[DateTime, Timestamp](
dateTime => new Timestamp(dateTime.getMillis),
timeStamp => new DateTime(timeStamp.getTime))

完整示例

case class Foo(str: String) //Foo needs Slick Mapping for below code to compile

implicit def fooMapping: BaseColumnType[Foo] = MappedColumnType.base[Foo, String](
str => Foo(str),
foo => foo.str)


case class Person(name: String, foo: Foo)

class Persons(tag) extends Table[Person](tag, "persons") {
  def name = column[String]("name")
  def foo = column[Foo]("foo") //use Foo directly because Implicit mapping is available in scope
  def * = (name, foo) <> (Person.tupled,  Person.unapply)
}

Answer 2

列的类型不是 column，而是 Rep。 column实际上是一个函数，告诉slick使用哪一列：

class BlockHeaderTable(tag: Tag) extends Table[BlockHeader](tag,"block_headers")  {

  def version: Rep[UInt32] = column[UInt32]("version")

  def previousBlockHash: Rep[DoubleSha256Digest] = column[DoubleSha256Digest]("previous_block_hash")

  ...
}

此外，我不确定您使用的是什么类型，但 slick see here 不支持开箱即用的类型。您将需要编写自定义类型映射器。例如 UInt32 映射器：

implicit val UInt32Mapper = MappedColumnType.base[UInt32, Long](
  u => u.toLong,                  // convert UInt32 to Long here
  l => UInt32(l)                  // and Long to UInt32 here
)

Slick 3.1.1 未找到类型 'column'

Slick 3.1.1 not found type 'column'

scala

slick