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10352 :: Call to parameterized protected constructor of a base class when interop with C++

• NikeKhin (orginal) [2023-07-24T10:26:51+02:00] view original

  Hello, the point is how to wrap a C++ base class with non-default protected constructor. Pure C++ use case is

  class Base{
  protected:
    Base(string name){
    }
  };
  class Derived : public Base {
  public:
    Derived(string name) : Base(name){
    }
  };
  Run

  In nim it is intended to be like

  type
    NimBase {.requiresInit, importcpp: "Base", header: "<systemc.h>", inheritable.} = object
    NimDerived = object of NimBase
  proc ConstructBase(T: typedesc[NimBase], name: cstring): NimBase {.importcpp: "Base(@)", constructor.}
  proc ConstructDerived(T: typedesc[NimDerived], name: cstring): NimDerived =
    discard ConstructBase(NimBase, name)
  
  var d : Derived = Derived.ConstructDerived("name of derived")
  Run

  After all the constructor ConstructBase is implemented in protected Base::Base C++ code and is not accessible. How can one make nim generate in C++ backend something like a code below? .. code-block:: cpp

  Derived(string name) : Base(name)

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• jmgomez (orginal) [2023-07-24T15:58:45+02:00] view original

  In 2.0 and devel you can use the expanded constructor pragma. There is a similar example in the docs: https://nim-lang.github.io/Nim/manual_experimental.html#constructor-pragma

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