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How to: Declare Interior Pointers with the const Keyword

The following sample shows how to use const in the declaration of an interior pointer.


// interior_ptr_const.cpp
// compile with: /clr
using namespace System;
value struct V { 
   int i;

ref struct G {
   V v;
   String ^ msg;

interior_ptr<int> f( interior_ptr<V> pv ) { 
   return &(pv->i); 

int main() {
   int n = -1;
   int o = -1;
   interior_ptr<int> pn1 = &n;
   *pn1 = 50;

   V v;
   v.i = 101;
   V * npV = &v;   // ok: &v yields a pointer to the native heap

   interior_ptr<int> pn2 = &n;
   interior_ptr<V> pV = &(v);
   pn2 = f(pV);
   *pn2 = 50;

   G ^pG = gcnew G;
   pV = &(pG->v);   // ok: pV is an interior pointer

   interior_ptr<int const> pn3 = &n;
   // *pn3 = 5;   error because pn3 cannot be dereferenced and changed
   pn3 = &o;   // OK, can change the memory location

   interior_ptr<int> const pn4 = &n;   
   *pn4 = 5;   // OK because you can dereference and change pn4
   // pn4 = &o;   error cannot change the memory location

   const interior_ptr<const int> pn5 = &n;
   // *pn5 = 5;   error cannot dereference and change pn5
   // pn5 = &o;   error cannot change the memory location

   const G ^ h_G = gcnew G;   // object is const, cannot modify any members of h_G or call any non-const methods
   // h_G->msg = "test";   error h_G is const
   interior_ptr<String^ const> int_ptr_G = &(h_G->msg);

   G ^ const h_G2 = gcnew G;   // interior pointers to this obejct cannot be dereferenced and changed
   h_G2->msg = "test";
   interior_ptr<String^ const> int_ptr_G2 = &(h_G->msg);

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