type-parameter – Tarik Billa

What’s wrong with this reflection code? GetFields() is returning an empty array

December 30, 2023 by Tarik

The parameterless GetFields() returns public fields. If you want non-public ones, use: cc.GetType().GetFields(BindingFlags.Instance | BindingFlags.NonPublic); or whatever appropriate combination you want – but you do need to specify at least one of Instance and Static, otherwise it won’t find either. You can specify both, and indeed public fields as well, to get everything: cc.GetType().GetFields(BindingFlags.Instance | … Read more

What is the difference between bounded wildcard and type parameters?

September 3, 2023 by Tarik

They expose different interfaces and contract for the method. The first declaration should return a collection whose elements type is the same of the argument class. The compiler infers the type of N (if not specified). So the following two statements are valid when using the first declaration: Collection<Integer> c1 = getThatCollection(Integer.class); Collection<Double> c2 = … Read more

Writing Algebraic Data Type in Scala

August 29, 2023 by Tarik

Defining an ADT In Scala’s “object-functional” model, you define a trait that represents the ADT and all of its parameters. Then for each of your cases, you define either a case class or a case object. Type and value parameters are treated as arguments to the class constructor. Typically, you make the trait sealed so … Read more

Scala – creating a type parametrized array of specified length

July 28, 2023 by Tarik

val chars = Array[Char](256) This works because 256 treated as a Char and it creates one-element array (with code 256) val len = 256 val chars = Array[Char](len) Here len is Int, so it fails To create array of specified size you need something like this val chars = Array.fill(256){0} where {0} is a function … Read more

How to instantiate an instance of type represented by type parameter in Scala

June 3, 2023 by Tarik

EDIT – apologies, I only just noticed your first error. There is no way of instantiating a T at runtime because the type information is lost when your program is compiled (via type erasure) You will have to pass in some factory to achieve the construction: class BalanceActor[T <: Actor](val fac: () => T) extends … Read more