auto_gcroot 類別

自動資源管理 （例如 auto_ptr 類別），可用來將虛擬句柄內嵌至原生類型。

語法

template<typename _element_type>
class auto_gcroot;

參數

_element_type
要內嵌的Managed型別。

成員

公用建構函式

名稱	描述
auto_gcroot::auto_gcroot	建構函式 auto_gcroot 。
auto_gcroot::~auto_gcroot	解 auto_gcroot 構函式。

公用方法

名稱	描述
auto_gcroot::attach	附加 auto_gcroot 至物件。
auto_gcroot::get	取得自主物件。
auto_gcroot::release	從 auto_gcroot 管理釋放物件。
auto_gcroot::reset	終結目前擁有的物件，並選擇性地擁有新的物件。
auto_gcroot::swap	以另一個 auto_gcroot交換物件。

公用運算子

名稱	描述
auto_gcroot::operator->	成員存取運算子。
auto_gcroot::operator=	指派運算子。
auto_gcroot::operator auto_gcroot	與相容型別之間的 auto_gcroot 類型轉換運算元。
auto_gcroot::operator bool	auto_gcroot在條件表達式中使用的運算符。
auto_gcroot::operator!	auto_gcroot在條件表達式中使用的運算符。

需求

頭檔<msclr\auto_gcroot.h>

命名空間 msclr

auto_gcroot::auto_gcroot

建構函式 auto_gcroot 。

auto_gcroot(
   _element_type _ptr = nullptr
);
auto_gcroot(
   auto_gcroot<_element_type> & _right
);
template<typename _other_type>
auto_gcroot(
   auto_gcroot<_other_type> & _right
);

參數

_ptr
要擁有的物件。

_右
現有的 auto_gcroot。

備註

從現有的 建構 auto_gcroot 時，現有的 auto_gcroot 會先釋放其 物件，再將 對象的擁有權傳送至新的 auto_gcroot。auto_gcroot

範例

// msl_auto_gcroot_auto_gcroot.cpp
// compile with: /clr
#include <msclr\auto_gcroot.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 );
   }
};

class ClassA { //unmanaged class
private:
   auto_gcroot<RefClassA^> m_a;

public:
   ClassA() : m_a( gcnew RefClassA( "unmanaged" ) ) {}
   ~ClassA() {} //no need to delete m_a

   void DoSomething() {
      m_a->PrintHello();
   }
};

int main()
{
   {
      ClassA a;
      a.DoSomething();
   } // a.m_a is automatically destroyed as a goes out of scope

   {
      auto_gcroot<RefClassA^> a(gcnew RefClassA( "first" ) );
      a->PrintHello();
   }

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

   Console::WriteLine("done");
}

in RefClassA constructor: unmanaged
Hello from unmanaged A!
in RefClassA destructor: unmanaged
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_gcroot::~auto_gcroot

解 auto_gcroot 構函式。

~auto_gcroot();

備註

解構函式也會解構擁有的物件。

範例

// msl_auto_gcroot_dtor.cpp
// compile with: /clr
#include <msclr\auto_gcroot.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_gcroot<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_gcroot::attach

附加 auto_gcroot 至物件。

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
);

參數

_右
要附加的物件，或 auto_gcroot 包含要附加之 物件的 。

傳回值

目前的 auto_gcroot。

備註

如果 _right 為 auto_gcroot，則會在物件附加至目前的 auto_gcroot之前釋放其 對象的擁有權。

範例

// 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

auto_gcroot::get

取得自主物件。

_element_type get() const;

傳回值

自主物件。

範例

// msl_auto_gcroot_get.cpp
// compile with: /clr
#include <msclr\auto_gcroot.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_gcroot<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_gcroot::release

從 auto_gcroot 管理釋放物件。

_element_type release();

傳回值

已發行的物件。

範例

// msl_auto_gcroot_release.cpp
// compile with: /clr
#include <msclr\auto_gcroot.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_gcroot<ClassA^> agc1 = gcnew ClassA( "first" );
      auto_gcroot<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_gcroot::reset

終結目前擁有的物件，並選擇性地擁有新的物件。

void reset(
   _element_type _new_ptr = nullptr
);

參數

_new_ptr
（選擇性）新的物件。

範例

// msl_auto_gcroot_reset.cpp
// compile with: /clr
#include <msclr\auto_gcroot.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_gcroot<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_gcroot::swap

以另一個 auto_gcroot交換物件。

void swap(
   auto_gcroot<_element_type> & _right
);

參數

_右
auto_gcroot要交換物件的 。

範例

// msl_auto_gcroot_swap.cpp
// compile with: /clr
#include <msclr\auto_gcroot.h>

using namespace System;
using namespace msclr;

int main() {
   auto_gcroot<String^> s1 = "string one";
   auto_gcroot<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_gcroot::operator->

成員存取運算子。

_element_type operator->() const;

傳回值

由 auto_gcroot包裝的物件。

範例

// msl_auto_gcroot_op_arrow.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 ) {}

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

   int m_i;
};

int main() {
   auto_gcroot<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_gcroot::operator=

指派運算子。

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

參數

_右
要指定給目前auto_gcroot的物件或 auto_gcroot 。

傳回值

目前的 auto_gcroot，現在擁有 _right。

範例

// msl_auto_gcroot_operator_equals.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;
   auto_gcroot<ClassA^> a2(gcnew ClassA( "first" ) );
   a = a2; // assign from same type
   a->PrintHello();

   ClassA^ ha = gcnew ClassA( "second" );
   a = ha; // assign from raw handle

   auto_gcroot<ClassB^> b(gcnew ClassB( "third" ) );
   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
in ClassA destructor: first
in ClassA constructor: third
Hello from third B!
in ClassA destructor: second
Hello from third A!
done
in ClassA destructor: third

auto_gcroot::operator auto_gcroot

與相容型別之間的 auto_gcroot 類型轉換運算元。

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

傳回值

目前 auto_gcroot 轉換成 auto_gcroot<_other_type>。

範例

// msl_auto_gcroot_op_auto_gcroot.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 ) {}

   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<ClassB^> b = gcnew ClassB("first");
   b->PrintHello();
   auto_gcroot<ClassA^> a = (auto_gcroot<ClassA^>)b;
   a->PrintHello();
}

Hello from first B!
Hello from first A!

auto_gcroot::operator bool

auto_gcroot在條件表達式中使用的運算符。

operator bool() const;

傳回值

true 如果包裝的物件有效，則為 ; false 否則。

備註

這個運算符實際上會轉換成 _detail_class::_safe_bool，這比 bool 無法轉換成整數類型更安全。

範例

// msl_auto_gcroot_operator_bool.cpp
// compile with: /clr
#include <msclr\auto_gcroot.h>

using namespace System;
using namespace msclr;

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

s is invalid
now s is valid
now s is invalid

auto_gcroot::operator!

auto_gcroot在條件表達式中使用的運算符。

bool operator!() const;

傳回值

true 如果包裝的物件無效，則為 ; false 否則。

範例

// msl_auto_gcroot_operator_not.cpp
// compile with: /clr
#include <msclr\auto_gcroot.h>

using namespace System;
using namespace msclr;

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

s is invalid
now s is valid
now s is invalid