auto_gcroot::attach

Article
06/05/2017

The new home for Visual Studio documentation is Visual Studio 2017 Documentation on docs.microsoft.com.

The latest version of this topic can be found at auto_gcroot::attach.

Attach auto_gcroot to an object.

Syntax

auto_gcroot<_element_type> & attach(  
   _element_type _right  
);  
auto_gcroot<_element_type> & attach(  
   auto_gcroot<_element_type> & _right  
);  
template<typename _other_type>  
auto_gcroot<_element_type> & attach(  
   auto_gcroot<_other_type> & _right  
);

Parameters

_right
The object to attach, or an auto_gcroot containing the object to attach.

Return Value

The current auto_gcroot.

Remarks

If _right is an auto_gcroot, it releases ownership of its object before the object is attached to the current auto_gcroot.

Example

// msl_auto_gcroot_attach.cpp  
// compile with: /clr  
#include <msclr\auto_gcroot.h>  
  
using namespace System;  
using namespace msclr;  
  
ref class ClassA {  
protected:     
   String^ m_s;  
public:  
   ClassA( String^ s ) : m_s( s ) {  
      Console::WriteLine( "in ClassA constructor:" + m_s );  
   }  
   ~ClassA() {  
      Console::WriteLine( "in ClassA destructor:" + m_s );  
   }  
  
   virtual void PrintHello() {  
      Console::WriteLine( "Hello from {0} A!", m_s );  
   }  
};  
  
ref class ClassB : ClassA {  
public:  
   ClassB( String ^ s) : ClassA( s ) {}  
   virtual void PrintHello() new {  
      Console::WriteLine( "Hello from {0} B!", m_s );  
   }  
};  
  
int main() {  
   auto_gcroot<ClassA^> a( gcnew ClassA( "first" ) );  
   a->PrintHello();  
   a.attach( gcnew ClassA( "second" ) ); // attach same type  
   a->PrintHello();  
   ClassA^ ha = gcnew ClassA( "third" );  
   a.attach( ha ); // attach raw handle  
   a->PrintHello();  
   auto_gcroot<ClassB^> b( gcnew ClassB("fourth") );  
   b->PrintHello();  
   a.attach( b ); // attach derived type  
   a->PrintHello();  
}

in ClassA constructor:first  
Hello from first A!  
in ClassA constructor:second  
in ClassA destructor:first  
Hello from second A!  
in ClassA constructor:third  
in ClassA destructor:second  
Hello from third A!  
in ClassA constructor:fourth  
Hello from fourth B!  
in ClassA destructor:third  
Hello from fourth A!  
in ClassA destructor:fourth

Requirements

Header file <msclr\auto_gcroot.h>

Namespace msclr

Share via