Question

我正在尝试在C ++中初始化对C＃传递的boost共享指针的引用，同时尝试维护继承树。我希望能够在C＃中创建一个变量，然后将其传递给我的DLL，它将在内部实例化它（这样我就可以在同一个上下文中管理所有内存分配）。

这是我的C ++测试用例（在文件SwigTest.h中）：

#include <string>
#include <boost/shared_ptr.hpp>

template<class T>
using SRef = boost::shared_ptr<T>;

class FactoryClass
{
   public:
      FactoryClass() {}
      ~FactoryClass() {}

      //Normally I would only like to use the return value, but SWIG uses polymorphism to simulate templates
      //and polymorphism on the return type only is not supported by C#. (I get a Identifier 'getReference' redefined error on SwigTest.i compilation).
      //So I thought I’d pass the SRef& as a parameter instead of having no parameters at all.
       template <class  T>
       static SRef<T> getReference( SRef<T>& inout ) { inout = SRef<T>( new T(1) ); return inout; }

       void testing( int& toto ) {};
};

class BaseClass
{
   public:
      BaseClass() { m_flag = -1; };
      BaseClass(int i) { m_flag = i; };
      virtual ~BaseClass() {};

      virtual std::string getName() = 0;

      int m_flag;
};

class FirstClass : public BaseClass
{
   public:
      FirstClass() {};
      FirstClass(int i) : BaseClass( i ) {};
      virtual ~FirstClass() {};

      virtual std::string getName() { return "First Class"; };
};

class SecondClass : public BaseClass
{
   public:
      SecondClass() {};
      SecondClass(int i) : BaseClass( i ) {};
      virtual ~SecondClass() {};

      virtual std::string getName() { return "Second Class"; };
};

这是我当前的SWIG界面文件：

%module SwigTest
%include "std_string.i"
%include "boost_shared_ptr.i"

%{
#include "../include/SwigTest.h"
%}

%shared_ptr( BaseClass );
%shared_ptr( FirstClass );
%shared_ptr( SecondClass );

%include "../include/SwigTest.h"

%template(BoostBasePtr) boost::shared_ptr<BaseClass>;
%template(SharedBase) SRef<BaseClass>;

%template(BoostFirstPtr) boost::shared_ptr<FirstClass>;
%template(SharedFirst)SRef<FirstClass>;
%template(getReference)FactoryClass::getReference<FirstClass>;

%template(BoostSecondPtr) boost::shared_ptr<SecondClass>;
%template(SharedSecond)SRef<SecondClass>;
%template(getReference)FactoryClass::getReference<SecondClass>;

这是C＃中的有效和无效的内容：

public class SwigInterface
{
   private FirstClass m_first;
   private SecondClass m_second = new SecondClass(-2);

   void TestSwig ()
   {
      m_first = FactoryClass.getReference( m_first ); //The returned reference is copied from C++
      FactoryClass.getReference( m_second ); //m_second is never changed

      FirstClass anotherFirst = new FirstClass(-1) ;
      BaseClass bc = FactoryClass.getReference( anotherFirst); //bc does equal the new instance of FirstClass but anotherFirst is not correctly replaced

       //This is the case I would ideally want to use
       SecondClass nothing ;
       FactoryClass.getReference( nothing ) ; //NullReferenceException (because the SWIG generated interface uses nothing.CPtr() to pass by pointer as it does with all refs).
    }
}

我尝试了很多%typename体操用FactoryClass.getReference( FirstClass )取代FactoryClass.getReference( out FirstClass )的签名（甚至是引用FirstClass），但我找不到合适的方法。< / p>

在一个完美的世界中，我只想在C＃中的FactoryClass中生成void getReference<T>( ref T inout )，但即使使用SWIG %extend关键字添加方法也不会生成它，因为我必须实例化我需要的每个模板。

Answer 1

如果我理解您的观点，那么您已达到SWIG限制。我遇到了同样的问题。每个指针（智能或非智能）在C＃中丢失一次多态性。

您需要使用％pragma（csharp）指令为C＃端的 BaseClass 提供特殊工厂。然后你需要用你的csout类型映射映射你的指针：

%typemap(csout, excode=SWIGEXCODE)
  BaseClass*, std::shared_ptr<BaseClass>, std::shared_ptr<BaseClass> & {
    System.IntPtr cPtr = $imcall;
    // The following line is a call to your special factory
    BaseClass ret = $imclassname.createBaseClass(cPtr, $owner);$excode
    return ret;
}

你的工厂可能是这样的：

%pragma(csharp) imclasscode=%{
    public static BaseClass createBaseClass(System.IntPtr cPtr, bool owner)
    {
        BaseClass ret = null;
        if (cPtr == System.IntPtr.Zero) {
          return ret;
        }
        string name = ($imclassname.BaseClass_getName(new System.Runtime.InteropServices.HandleRef(null, cPtr)));
        switch (name)
        {
        case "First Class":
            return new FirstClass(cPtr, owner);
        case "Second Class":
            return new SecondClass(cPtr, owner);
        default:
            return null;
        }
    }
%}

我没有对它进行测试，也许有些事情要改变或适应。但它应该有用。

使用SWIG初始化对来自C ++的C＃共享指针的引用

1 个答案: