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How can a generic interface refer to a pointer to its type parameter?


How can a generic interface refer to a pointer to its type parameter?

By : Payam Shahidi
Date : November 22 2020, 02:42 PM
hop of those help? In an ideal world, you would be able to declare a generic pointer type directly:
code :
type
  P<T> = ^T;
type
  PointerTo<T> = record
    type
      P = ^T;
  end;
type
  ITable<T> = interface
    function Append: PointerTo<T>.P;
  end;


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Refer generic without type parameter in Scala

Refer generic without type parameter in Scala


By : 孙林伟
Date : March 29 2020, 07:55 AM
This might help you I believe I can achieve your aim, but using type members rather than type parameters.
Also, this meant I could move the implementation of addChild into the trait and not re-implement it in the subclasses.
code :
trait TreeNode {
  type ChildType <: NonRootNode
  val children:HashSet[ChildType] = new HashSet[ChildType]
  def addChild(c:ChildType) = {
    children.add(c)
  }
}

abstract class NonRootNode extends TreeNode {
  var passengers:Set[Passenger] = Set()
}

case object RootNode extends TreeNode { type ChildType = TimeNode }

trait IntervalMarker

case class TimeNode(time:Int) extends NonRootNode with IntervalMarker { type ChildType = StartNode }

case class StartNode(l:Option[String]) extends NonRootNode with IntervalMarker { type ChildType = EndNode }

case class EndNode(l:Option[String]) extends NonRootNode { type ChildType = NonRootNode with IntervalMarker }
Scala: refer to nested type of class, which comes as type parameter to generic

Scala: refer to nested type of class, which comes as type parameter to generic


By : user2855261
Date : March 29 2020, 07:55 AM
it should still fix some issue I want to implement class, which describes action about setting some option value. I want to make option 's value type be depent of option type. I am trying to make this: , Type member
code :
case class SetOptionMessage[V, T <: BaseOptionType{ type ValueType = V }](
  option: T,
  value: Option[V]
)

val msg = SetOptionMessage(SomeBooleanOption, Some(true))
// msg: SetOptionMessage[Boolean,SomeBooleanOption.type] = SetOptionMessage(SomeBooleanOption$@2e93ebe0,Some(true))
case class SetOptionMessage[V, T <: BaseOptionType](
  option: T,
  value: Option[V])(implicit e: V =:= T#ValueType)

SetOptionMessage(SomeBooleanOption, Some(true))
// SetOptionMessage[Boolean,SomeBooleanOption.type] = SetOptionMessage(SomeBooleanOption$@2e93ebe0,Some(true))

SetOptionMessage(SomeBooleanOption, None)
// SetOptionMessage[SomeBooleanOption.ValueType,SomeBooleanOption.type] = SetOptionMessage(SomeBooleanOption$@2e93ebe0,None)
class SetOptionMessage[T <: BaseOptionType](option: T)(val value: Option[T#ValueType])

val msg = new SetOptionMessage(SomeBooleanOption)(Some(true))
// SetOptionMessage[SomeBooleanOption.type] = SetOptionMessage@7f216e0c

msg.value
// Option[SomeBooleanOption.ValueType] = Some(true)
Commenting Generics - Is it possible to refer to generic type parameter not as T but as its actual type?

Commenting Generics - Is it possible to refer to generic type parameter not as T but as its actual type?


By : ZachRNZ
Date : March 29 2020, 07:55 AM
wish help you to fix your issue No, Visual Studio does not support that. You should ask yourself why you would want to use the specific type in your comments.
A good method documentation is done by describing it function in non-technical terms. And describe its parameters by using clear names and a good description what is expected of that parameter. The type is hardly ever need. If you do need it, you probably are trying to document your methods in a thechnical way, which is hardly ever a good idea.
How to refer to the value of a type parameter in a generic method

How to refer to the value of a type parameter in a generic method


By : Beaula Antony
Date : March 29 2020, 07:55 AM
To fix the issue you can do You can't. Only classes can be used as values. Other types, generic parameters in particular, are not values, they are not preserved when typescript is compiled to javascript. That variable must be provided explicitly to loadChunk() somehow, either as value argument similar to CreateItem(), or accessible as a property of Catalog class, which in turn must be initialized somehow.
See also Do Typescript generics use type erasure to implement generics?.
Get type that implements generic interface by searching for a specific generic interface parameter

Get type that implements generic interface by searching for a specific generic interface parameter


By : Jason Sprague
Date : March 29 2020, 07:55 AM
I hope this helps you . I'd like to create a method that returns a type (or IEnumerable of types) that implement a specific interface that takes a type parameter -- however I want to search by that generic type parameter itself. This is easier demonstrated as an example: , You can try like this;
code :
    public static IEnumerable<Type> GetByInterfaceAndGeneric(Type interfaceWithParam, Type specificTypeParameter)
    {
        var query =  
            from x in specificTypeParameter.Assembly.GetTypes()
            where 
            x.GetInterfaces().Any(k => k.Name == interfaceWithParam.Name && 
            k.Namespace == interfaceWithParam.Namespace && 
            k.GenericTypeArguments.Contains(specificTypeParameter))
            select x;
        return query;
    }
var types = GetByInterfaceAndGeneric(typeof(IRepository<>), typeof(Foo)).ToList();
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