visual c++ - How to wrap class that passes unmanaged class in constructor? -

i trying understand c++/cli can create wrapper classes c++ code. problem have class stores pointer parent object of class, therefore need pass class.

below example, full class has more functions , stores data.

class { private:     a* parent;  public:     a(a* parent)     {         parent = parent;     }     ~a()     {         delete parent;     }      a* getparent()     {         return parent;     } } 

my current idea have non-public constructor can construct managed class unmanaged 1 without being accessible outside class.

public ref class manageda {     a* unmanaged;      manageda(a* unmanaged)     {         this->unmanaged = unmanaged;     }  public:     manageda(manageda^ parent)     {         unmanaged = new a(parent->unmanaged);     }      ~manageda()     {         delete unmanaged;         unmanaged = null;     }      manageda^ getparent()     {         return gcnew manageda(unmanaged->getparent());     } } 

while works functions inside class, still have issues if want create object or if have function needs unmanaged class passed in.

is there way can work around this?

manageda^ getparent() {     return gcnew manageda(unmanaged->getparent()); } 

you shooting leg off code this, very dangerous. problem is, creating multiple manageda objects refer exact same a*. one of them gets destroyed, other manageda objects have dangling pointer. that's guaranteed cause memory corruption.

the solution simple, store parent reference in constructor:

public ref class manageda { private:     a* unmanaged;     manageda^ parent; public:     manageda(manageda^ parent) : parent(parent) {         a* unmanagedparent = parent == nullptr ? nullptr : parent->unmanaged;         unmanaged = new a(unmanagedparent);     }     manageda^ getparent() {         return parent;     }     ~manageda() {         this->!manageda();         unmanaged = null;     }     !manageda() {         delete unmanaged;     } }; 

note added nullptr check in constructor, sane way see how first a* ever created.

that easy case, exact same object identity problem occurs when ever need map a* manageda^. first check if really needed, client code expected ever manipulate manageda objects. when necessary, you'll need create lookup table can reliably find corresponding manageda^ back. requires static dictionary<intptr, manageda^>. add objects dictionary in constructor, remove them in finalizer. note forgot include finalizer, not optional. added snippet.