我看过特拉维斯·布朗（Travis Brown）提出的炫酷solution，它允许以通用方式在彼此之间转换案例类。我尝试使用它将 HttpListener listener2 = new HttpListener();
listener2.Prefixes.Clear();
listener2.Prefixes.Add("http://+:4200/");
listener2.Prefixes.Add("http://XXX.XXX.eu/");
listener2.Start();
LogWriteLine("http listener started listening to: " +listener2.Prefixes);
try
{
while (true)//change to match end check
{
LogWriteLine("http listener waiting");
HttpListenerContext context = listener2.GetContext();
LogWriteLine("http request arrived");
HttpListenerRequest request = context.Request;
// Obtain a response object.
HttpListenerResponse response = context.Response;
System.IO.Stream body = request.InputStream;
System.Text.Encoding encoding = request.ContentEncoding;
System.IO.StreamReader reader = new System.IO.StreamReader(body, encoding);
if (!request.HasEntityBody)
{
LogWriteLine("No client data was sent with the request.");
Thread.Sleep(300);
//return;
}
if (request.ContentType != null)
{
LogWriteLine("Client data content type " + request.ContentType);
}
LogWriteLine("Client data content length " + request.ContentLength64); //Works fine
LogWriteLine("Start of client data:");
// Convert the data to a string and display it on the console.
Console.WriteLine(body.CanSeek);
string s = reader.ReadToEnd();
var ahoj = new StreamReader(context.Request.InputStream).ReadToEnd();
Console.WriteLine("ahoj length " + ahoj.Length); //0
Console.WriteLine(s); //nothing
string text;
var bytes = default(byte[]);
using (var reader1 = new StreamReader(request.InputStream,
request.ContentEncoding))
{
text = reader1.ReadToEnd();
Console.WriteLine(text + text.Length); //output: 0
using (var memstream = new MemoryStream())
{
reader1.BaseStream.CopyTo(memstream);
bytes = memstream.ToArray();
}
Console.WriteLine("bytes:" + bytes.Length); //output: bytes: 0
}
LogWriteLine("End of client data:");
//write to console file
sw.Write(s);
body.Close();
reader.Close();
}
}
catch (Exception ex)
{
Console.WriteLine(ex);
}
转换为HList，但没有设法使其正常工作。这是我的尝试：
case class不幸的是，它失败并显示以下错误：
import shapeless._, ops.hlist.Align
import syntax.std.tuple._
object Shplss extends App {
class SameFieldsConverter[T] {
def apply[S, SR <: HList, TR <: HList](s: S)(implicit
genS: LabelledGeneric.Aux[S, SR],
genT: LabelledGeneric.Aux[T, TR],
align: Align[SR, TR]
) = genT.from(align(genS.to(s)))
}
def convertTo[T] = new SameFieldsConverter[T]
type SomeType = Int :: Int :: String :: Boolean :: Int :: Int :: HNil
final case class SomeProductType(f1: Int, f2: Int, f3: String, f4: Boolean, f5: Int, f6: Int)
val some: SomeType = (4, 4, "ssdf", true, 2, 4).productElements
convertTo[SomeProductType](some)
}
是否有一种增强Error:(22, 29) could not find implicit value for parameter genS: shapeless.LabelledGeneric.Aux[com.test.Shplss.SomeType,SR]
convertTo[SomeProductType](some)
Error:(22, 29) not enough arguments for method apply: (implicit genS: shapeless.LabelledGeneric.Aux[com.test.Shplss.SomeType,SR], implicit genT: shapeless.LabelledGeneric.Aux[com.test.Shplss.SomeProductType,TR], implicit align: shapeless.ops.hlist.Align[SR,TR])com.test.Shplss.SomeProductType in class SameFieldsConverter.
Unspecified value parameters genS, genT, align.
convertTo[SomeProductType](some)
函数的方法，使其也可以在converTo[B]之间转换？
答案 0 :(得分：5)
Shapeless的Generic和LabelledGeneric是类型类，它们为使用hlists和coproducts的案例类和密封特性层次提供通用表示。如果您已经有了一个hlist，则实际上不需要Generic实例，而Shapeless不提供实例。就您而言，这意味着您实际上可以跳过genS和SR部分：
import shapeless._, ops.hlist.Align
import syntax.std.tuple._
object Shplss extends App {
class SameFieldsConverter[T] {
def apply[S <: HList, TR <: HList](s: S)(implicit
genT: Generic.Aux[T, TR],
align: Align[S, TR]
) = genT.from(align(s))
}
def convertTo[T] = new SameFieldsConverter[T]
type SomeType = Int :: Int :: String :: Boolean :: Int :: Int :: HNil
final case class SomeProductType(f1: Int, f2: Int, f3: String, f4: Boolean, f5: Int, f6: Int)
val some: SomeType = (4, 4, "ssdf", true, 2, 4).productElements
convertTo[SomeProductType](some)
}
这将给您SomeProductType(4,4,ssdf,true,2,4)，如您所愿。
请注意，由于我们不再具有要在输入侧对齐的标签，因此我已将genT从LabelledGeneric更改为Generic。我猜您可以添加一些额外的机制来将未标记的输入“注入”到Shapeless记录中，以匹配LabelledGeneric类型，但是在这种特定的用例中，至少没有任何意义。