auto_handle-Klasse

Automatische Ressourcenverwaltung, die zum Einbetten eines virtuellen Handles in einen verwalteten Typ verwendet werden kann.

Syntax

template<typename _element_type>
ref class auto_handle;

Parameter

_element_type
Der verwaltete Typ, der eingebettet werden soll.

Member

Öffentliche Konstruktoren

Öffentliche Methoden

Öffentliche Operatoren

Anforderungen

Headerdatei<msclr\auto_handle.h>

Namespace msclr

auto_handle::auto_handle

Der auto_handle Konstruktor.

auto_handle();
auto_handle(
   _element_type ^ _ptr
);
auto_handle(
   auto_handle<_element_type> % _right
);
template<typename _other_type>
auto_handle(
   auto_handle<_other_type> % _right
);

Parameter

_ptr
Das zu besitzende Objekt.

_Rechts
Ein vorhandener auto_handle.

Beispiel

// msl_auto_handle_auto_handle.cpp
// compile with: /clr
#include "msclr\auto_handle.h"

using namespace System;
using namespace msclr;
ref class RefClassA {
protected:
   String^ m_s;
public:
   RefClassA(String^ s) : m_s(s) {
      Console::WriteLine( "in RefClassA constructor: " + m_s );
   }
   ~RefClassA() {
      Console::WriteLine( "in RefClassA destructor: " + m_s );
   }

   virtual void PrintHello() {
      Console::WriteLine( "Hello from {0} A!", m_s );
   }
};

ref class RefClassB : RefClassA {
public:
   RefClassB( String^ s ) : RefClassA( s ) {}
   virtual void PrintHello() new {
      Console::WriteLine( "Hello from {0} B!", m_s );
   }
};

int main()
{
   {
      auto_handle<RefClassA> a(gcnew RefClassA( "first" ) );
      a->PrintHello();
   }

   {
      auto_handle<RefClassB> b(gcnew RefClassB( "second" ) );
      b->PrintHello();
      auto_handle<RefClassA> a(b); //construct from derived type
      a->PrintHello();
      auto_handle<RefClassA> a2(a); //construct from same type
      a2->PrintHello();
   }

   Console::WriteLine("done");
}

in RefClassA constructor: first
Hello from first A!
in RefClassA destructor: first
in RefClassA constructor: second
Hello from second B!
Hello from second A!
Hello from second A!
in RefClassA destructor: second
done

auto_handle::~auto_handle

Der auto_handle Destruktor.

~auto_handle();

Hinweise

Der Destruktor destruktiert auch das besitzeigene Objekt.

Beispiel

// msl_auto_handle_dtor.cpp
// compile with: /clr
#include "msclr\auto_handle.h"

using namespace System;
using namespace msclr;

ref class ClassA {
public:
   ClassA() { Console::WriteLine( "ClassA constructor" ); }
   ~ClassA() { Console::WriteLine( "ClassA destructor" ); }
};

int main()
{
   // create a new scope for a:
   {
      auto_handle<ClassA> a = gcnew ClassA;
   }
   // a goes out of scope here, invoking its destructor
   // which in turns destructs the ClassA object.

   Console::WriteLine( "done" );
}

ClassA constructor
ClassA destructor
done

auto_handle::get

Ruft das enthaltene Objekt ab.

_element_type ^ get();

Rückgabewert

Das enthaltene Objekt.

Beispiel

// msl_auto_handle_get.cpp
// compile with: /clr
#include "msclr\auto_handle.h"

using namespace System;
using namespace msclr;

ref class ClassA {
   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 );
   }

   void PrintHello() {
      Console::WriteLine( "Hello from {0} A!", m_s );
   }
};

void PrintA( ClassA^ a ) {
   a->PrintHello();
}

int main() {
   auto_handle<ClassA> a = gcnew ClassA( "first" );
   a->PrintHello();

   ClassA^ a2 = a.get();
   a2->PrintHello();

   PrintA( a.get() );
}

in ClassA constructor:first
Hello from first A!
Hello from first A!
Hello from first A!
in ClassA destructor:first

auto_handle::release

Gibt das Objekt aus der auto_handle Verwaltung frei.

_element_type ^ release();

Rückgabewert

Das freigegebene Objekt.

Beispiel

// msl_auto_handle_release.cpp
// compile with: /clr
#include <msclr\auto_handle.h>

using namespace System;
using namespace msclr;

ref class ClassA {
   String^ m_s;
public:
   ClassA( String^ s ) : m_s( s ) {
      Console::WriteLine( "ClassA constructor: " + m_s );
   }
   ~ClassA() {
      Console::WriteLine( "ClassA destructor: " + m_s );
   }

   void PrintHello() {
      Console::WriteLine( "Hello from {0} A!", m_s );
   }
};

int main()
{
   ClassA^ a;

   // create a new scope:
   {
      auto_handle<ClassA> agc1 = gcnew ClassA( "first" );
      auto_handle<ClassA> agc2 = gcnew ClassA( "second" );
      a = agc1.release();
   }
   // agc1 and agc2 go out of scope here

   a->PrintHello();

   Console::WriteLine( "done" );
}

ClassA constructor: first
ClassA constructor: second
ClassA destructor: second
Hello from first A!
done

auto_handle::reset

Zerstören Sie das aktuelle Objekt, und übernehmen Sie optional den Besitz eines neuen Objekts.

void reset(
   _element_type ^ _new_ptr
);
void reset();

Parameter

_new_ptr
(Optional) Das neue Objekt.

Beispiel

// msl_auto_handle_reset.cpp
// compile with: /clr
#include <msclr\auto_handle.h>

using namespace System;
using namespace msclr;

ref class ClassA {
   String^ m_s;
public:
   ClassA( String^ s ) : m_s( s ) {
      Console::WriteLine( "ClassA constructor: " + m_s );
   }
   ~ClassA() {
      Console::WriteLine( "ClassA destructor: " + m_s );
   }

   void PrintHello() {
      Console::WriteLine( "Hello from {0} A!", m_s );
   }
};

int main()
{
   auto_handle<ClassA> agc1 = gcnew ClassA( "first" );
   agc1->PrintHello();

   ClassA^ ha = gcnew ClassA( "second" );
   agc1.reset( ha ); // release first object, reference second
   agc1->PrintHello();

   agc1.reset(); // release second object, set to nullptr

   Console::WriteLine( "done" );
}

ClassA constructor: first
Hello from first A!
ClassA constructor: second
ClassA destructor: first
Hello from second A!
ClassA destructor: second
done

auto_handle::swap

Tauscht Objekte mit einem anderen auto_handle.

void swap(
   auto_handle<_element_type> % _right
);

Parameter

_Rechts
Das auto_handle Objekt, mit dem Objekte ausgetauscht werden sollen.

Beispiel

// msl_auto_handle_swap.cpp
// compile with: /clr
#include <msclr\auto_handle.h>

using namespace System;
using namespace msclr;

int main() {
   auto_handle<String> s1 = "string one";
   auto_handle<String> s2 = "string two";

   Console::WriteLine( "s1 = '{0}', s2 = '{1}'",
      s1->ToString(), s2->ToString() );
   s1.swap( s2 );
   Console::WriteLine( "s1 = '{0}', s2 = '{1}'",
      s1->ToString(), s2->ToString() );
}

s1 = 'string one', s2 = 'string two'
s1 = 'string two', s2 = 'string one'

auto_handle::operator->

Der Memberzugriffsoperator.

_element_type ^ operator->();

Rückgabewert

Das Objekt, das umschlossen ist auto_handle.

Beispiel

// msl_auto_handle_op_arrow.cpp
// compile with: /clr
#include <msclr\auto_handle.h>

using namespace System;
using namespace msclr;

ref class ClassA {
protected:
   String^ m_s;
public:
   ClassA( String^ s ) : m_s( s ) {}

   virtual void PrintHello() {
      Console::WriteLine( "Hello from {0} A!", m_s );
   }

   int m_i;
};

int main() {
   auto_handle<ClassA> a( gcnew ClassA( "first" ) );
   a->PrintHello();

   a->m_i = 5;
   Console::WriteLine( "a->m_i = {0}", a->m_i );
}

Hello from first A!
a->m_i = 5

auto_handle::operator=

Zuweisungsoperator.

auto_handle<_element_type> % operator=(
   auto_handle<_element_type> % _right
);
template<typename _other_type>
auto_handle<_element_type> % operator=(
   auto_handle<_other_type> % _right
);

Parameter

_Rechts
Der auto_handle dem aktuellen auto_handleElement zugewiesen werden soll.

Rückgabewert

Die aktuelle auto_handle, jetzt besitzen _right.

Beispiel

// msl_auto_handle_op_assign.cpp
// compile with: /clr
#include <msclr\auto_handle.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_handle<ClassA> a;
   auto_handle<ClassA> a2(gcnew ClassA( "first" ) );
   a = a2; // assign from same type
   a->PrintHello();

   auto_handle<ClassB> b(gcnew ClassB( "second" ) );
   b->PrintHello();
   a = b; // assign from derived type
   a->PrintHello();

   Console::WriteLine("done");
}

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

auto_handle::operator auto_handle

Typ-Umwandlungsoperator zwischen auto_handle und kompatiblen Typen.

template<typename _other_type>
operator auto_handle<_other_type>();

Rückgabewert

Die aktuelle auto_handle Umwandlung in auto_handle<_other_type>.

Beispiel

// msl_auto_handle_op_auto_handle.cpp
// compile with: /clr
#include <msclr\auto_handle.h>

using namespace System;
using namespace msclr;

ref class ClassA {
protected:
   String^ m_s;
public:
   ClassA( String^ s ) : m_s( 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_handle<ClassB> b = gcnew ClassB("first");
   b->PrintHello();
   auto_handle<ClassA> a = (auto_handle<ClassA>)b;
   a->PrintHello();
}

Hello from first B!
Hello from first A!

auto_handle::operator bool

Operator für die Verwendung auto_handle in einem bedingten Ausdruck.

operator bool();

Rückgabewert

true wenn das umschlossene Objekt gültig ist; false sonst.

Hinweise

Dieser Operator konvertiert tatsächlich, was _detail_class::_safe_bool sicherer ist, als bool weil er nicht in einen integralen Typ konvertiert werden kann.

Beispiel

// msl_auto_handle_operator_bool.cpp
// compile with: /clr
#include <msclr\auto_handle.h>

using namespace System;
using namespace msclr;

int main() {
   auto_handle<String> s1;
   auto_handle<String> s2 = "hi";
   if ( s1 ) Console::WriteLine( "s1 is valid" );
   if ( !s1 ) Console::WriteLine( "s1 is invalid" );
   if ( s2 ) Console::WriteLine( "s2 is valid" );
   if ( !s2 ) Console::WriteLine( "s2 is invalid" );
   s2.reset();
   if ( s2 ) Console::WriteLine( "s2 is now valid" );
   if ( !s2 ) Console::WriteLine( "s2 is now invalid" );
}

s1 is invalid
s2 is valid
s2 is now invalid

auto_handle::operator!

Operator für die Verwendung auto_handle in einem bedingten Ausdruck.

bool operator!();

Rückgabewert

true wenn das umschlossene Objekt ungültig ist; false sonst.

Beispiel

// msl_auto_handle_operator_not.cpp
// compile with: /clr
#include <msclr\auto_handle.h>

using namespace System;
using namespace msclr;

int main() {
   auto_handle<String> s1;
   auto_handle<String> s2 = "something";
   if ( s1) Console::WriteLine( "s1 is valid" );
   if ( !s1 ) Console::WriteLine( "s1 is invalid" );
   if ( s2 ) Console::WriteLine( "s2 is valid" );
   if ( !s2 ) Console::WriteLine( "s2 is invalid" );
   s2.reset();
   if ( s2 ) Console::WriteLine( "s2 is now valid" );
   if ( !s2 ) Console::WriteLine( "s2 is now invalid" );
}

s1 is invalid
s2 is valid
s2 is now invalid