How to: Declare Value Types with the interior_ptr Keyword (C++/CLI)
The latest version of this topic can be found at How to: Declare Value Types with the interior_ptr Keyword (C++/CLI).
An interior_ptr can be used with a value type.
Important
This language feature is supported by the /clr compiler option, but not by the /ZW compiler option.
Example
Description
The following C++/CLI sample shows how to use an interior_ptr with a value type.
Code
// interior_ptr_value_types.cpp
// compile with: /clr
value struct V {
V(int i) : data(i){}
int data;
};
int main() {
V v(1);
System::Console::WriteLine(v.data);
// pointing to a value type
interior_ptr<V> pv = &v;
pv->data = 2;
System::Console::WriteLine(v.data);
System::Console::WriteLine(pv->data);
// pointing into a value type
interior_ptr<int> pi = &v.data;
*pi = 3;
System::Console::WriteLine(*pi);
System::Console::WriteLine(v.data);
System::Console::WriteLine(pv->data);
}
Output
1
2
2
3
3
3
Example
Description
In a value type, the this pointer evaluates to an interior_ptr.
In the body of a non-static member-function of a value type V, this is an expression of type interior_ptr<V> whose value is the address of the object for which the function is called.
Code
// interior_ptr_value_types_this.cpp
// compile with: /clr /LD
value struct V {
int data;
void f() {
interior_ptr<V> pv1 = this;
// V* pv2 = this; error
}
};
Example
Description
The following sample shows how to use the address-of operator with static members.
The address of a static Visual C++ type member yields a native pointer. The address of a static value type member is a managed pointer because value type member is allocated on the runtime heap and can be moved by the garbage collector.
Code
// interior_ptr_value_static.cpp
// compile with: /clr
using namespace System;
value struct V { int i; };
ref struct G {
static V v = {22};
static int i = 23;
static String^ pS = "hello";
};
int main() {
interior_ptr<int> p1 = &G::v.i;
Console::WriteLine(*p1);
interior_ptr<int> p2 = &G::i;
Console::WriteLine(*p2);
interior_ptr<String^> p3 = &G::pS;
Console::WriteLine(*p3);
}
Output
22
23
hello