Scala 带反射的泛型参数的改进

下面是我目前正在处理的Http客户端的简化：

class Request[A]( val url: String, val event: Callbacks[A] )
{
    def run: Try[A] = ...
}
case class Image( override val url: String, override val event: Callbacks[Bitmap] ) extends Request[Bitmap]

---

我希望改进我的API，使

GET

调用如下：

GET[Image]( "http://...", null )

object GET {
  def apply[C <: Content](url: String, event: Callbacks[C])
                         (implicit rb: RequestBuilder[C]): C = {
    rb.create(url, event).run
  }
}

object HttpClient extends App {
  import ImplicitContainer._

  val bitmap = GET[Bitmap]("http://...", null)
  println(bitmap)
}

---

提供泛型参数

Image

应该意味着我正在使用

位图

，因此我不想再次指定它。

我能得到的最接近的方法是提供一个隐式参数，并将所有结果映射器（图像、Html等）注册为隐式值。由于额外的隐式定义，这会增加一些配置开销，但会产生更好的定制优势。这样我也摆脱了反射部分

implicit val image = Image.apply _

---

---

---

您可以使用类似于

CanBuildFrom

：使用隐式生成器创建合适的

请求的模式：

某些类型：

abstract class Content

class Bitmap extends Content

class Callbacks[T]

abstract class Request[C <: Content](val url: String, val event: Callbacks[C]) {
  def run: C
}

class ImageRequest(_url: String, _event: Callbacks[Bitmap]) 
  extends Request[Bitmap](_url, _event) {

  def run: Bitmap = {
    new Bitmap()
  }
}

要像这样使用：

GET[Image]( "http://...", null )

object GET {
  def apply[C <: Content](url: String, event: Callbacks[C])
                         (implicit rb: RequestBuilder[C]): C = {
    rb.create(url, event).run
  }
}

object HttpClient extends App {
  import ImplicitContainer._

  val bitmap = GET[Bitmap]("http://...", null)
  println(bitmap)
}

对象获取{
def应用[C]
abstract class Content

class Bitmap extends Content

class Callbacks[T]

abstract class Request[C <: Content](val url: String, val event: Callbacks[C]) {
  def run: C
}

class ImageRequest(_url: String, _event: Callbacks[Bitmap]) 
  extends Request[Bitmap](_url, _event) {

  def run: Bitmap = {
    new Bitmap()
  }
}

abstract class RequestBuilder[C <: Content] {
  def create(url: String, event: Callbacks[C]): Request[C]
}

class ImageRequestBuilder extends RequestBuilder[Bitmap]() {
  def create(url: String, event: Callbacks[Bitmap]): ImageRequest = {
    new ImageRequest(url, event)
  }
}

object ImplicitContainer {
  implicit val ImplicitImageRequestBuilder = new ImageRequestBuilder()
}

object GET {
  def apply[C <: Content](url: String, event: Callbacks[C])
                         (implicit rb: RequestBuilder[C]): C = {
    rb.create(url, event).run
  }
}

object HttpClient extends App {
  import ImplicitContainer._

  val bitmap = GET[Bitmap]("http://...", null)
  println(bitmap)
}