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Important This document may not represent best practices for current development, links to downloads and other resources may no longer be valid. Current recommended version can be found here.

How to: Using Tracking References and Interior Pointers

The following sample shows that taking the address of a tracking reference returns an interior_ptr and how to modify and access data through a tracking reference.

// tracking_reference_data.cpp
// compile with: /clr
using namespace System;

public ref class R {
public:
   R(int i) : m_i(i) {
      Console::WriteLine("ctor: R(int)");
   }

   int m_i;
};

class N {
public:
   N(int i) : m_i (i) {
      Console::WriteLine("ctor: N(int i)");
   }

   int m_i;
};

int main() {
   R ^hr = gcnew R('r');
   R ^%thr = hr;
   N n('n');
   N %tn = n;

   // Declare interior pointers
   interior_ptr<R^> iphr = &thr;
   interior_ptr<N> ipn = &tn;

   // Modify data through interior pointer
   (*iphr)->m_i = 1;   // (*iphr)->m_i == thr->m_i
   ipn->m_i = 4;   // ipn->m_i == tn.m_i
   
   ++thr-> m_i;   // hr->m_i == thr->m_i
   ++tn. m_i;   // n.m_i == tn.m_i
   
   ++hr-> m_i;   // (*iphr)->m_i == hr->m_i
   ++n. m_i;   // ipn->m_i == n.m_i
}

Output

ctor: R(int)
ctor: N(int i)

The following code sample shows that you can convert between tracking references and interior pointers.

// tracking_reference_interior_ptr.cpp
// compile with: /clr
using namespace System;

public ref class R {
public:
   R(int i) : m_i(i) {
      Console::WriteLine("ctor: R(int)");
   }

   int m_i;
};

class N {
public:
   N(int i) : m_i(i) {
      Console::WriteLine("ctor: N(int i)");
   }

   int m_i;
};

int main() {
   R ^hr = gcnew R('r');
   N n('n');

   R ^%thr = hr;
   N %tn = n;

   // Declare interior pointers
   interior_ptr<R^> iphr = &hr;
   interior_ptr<N> ipn = &n;

   // Modify data through interior pointer
   (*iphr)->m_i = 1;   // (*iphr)-> m_i == thr->m_i
   ipn->m_i = 4;   // ipn->m_i == tn.m_i

   ++thr->m_i;   // hr->m_i == thr->m_i
   ++tn.m_i;   // n.m_i == tn.m_i

   ++hr->m_i;   // (*iphr)->m_i == hr->m_i
   ++n.m_i;   // ipn->m_i == n.m_i
}

Output

ctor: R(int)
ctor: N(int i)

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