CAdapt Class

This template is used to wrap classes that redefine the address-of operator to return something other than the address of the object.

Syntax

template <class T>
class CAdapt

Parameters

T
The adapted type.

Members

Public Constructors

Public Operators

Public Data Members

Remarks

CAdapt is a simple template used to wrap classes that redefine the address-of operator (operator &) to return something other than the address of the object. Examples of such classes include ATL's CComBSTR, CComPtr, and CComQIPtr classes, and the compiler COM support class, _com_ptr_t. These classes all redefine the address-of operator to return the address of one of their data members (a BSTR in the case of CComBSTR, and an interface pointer in the case of the other classes).

CAdapt's primary role is to hide the address-of operator defined by class T, yet still retain the characteristics of the adapted class. CAdapt fulfils this role by holding a public member, m_T, of type T, and by defining conversion operators, comparison operators, and a copy constructor to allow specializations of CAdapt to be treated as if they are objects of type T.

The adapter class CAdapt is useful because some container-style classes expect to be able to obtain the addresses of their contained objects using the address-of operator. The redefinition of the address-of operator can confound this requirement, typically causing compilation errors and preventing the use of the non-adapted type with classes that expect it to "just work". CAdapt provides a way around those problems.

Typically, you will use CAdapt when you want to store CComBSTR, CComPtr, CComQIPtr, or _com_ptr_t objects in a container-style class. This was most commonly necessary for C++ Standard Library containers prior to support for the C++11 Standard, but C++11 Standard Library containers automatically work with types that have overloaded operator&(). The Standard Library achieves this by internally using std::addressof to get the true addresses of objects.

Requirements

Header: atlcomcli.h

CAdapt::CAdapt

The constructors allow an adapter object to be default constructed, copied from an object of the adapted type, or copied from another adapter object.

CAdapt();
CAdapt(const T& rSrc);
CAdapt(const CAdapt& rSrCA);
CAdapt(T&& rSrCA);  // (Visual Studio 2017)
CAdapt(CAdapt<T>&& rSrCA) noexcept; // (Visual Studio 2017)

Parameters

rSrc
A variable of the type being adapted to be copied into the newly constructed adapter object.

rSrCA
An adapter object whose contained data should be copied (or moved) into the newly constructed adapter object.

CAdapt::m_T

Holds the data being adapted.

T m_T;

Remarks

This public data member can be accessed directly or indirectly with operator const T& and operator T&.

CAdapt::operator const T&

Returns a const reference to the m_T member, allowing the adapter object to be treated as if it were an object of type T.

operator const T&() const;

Return Value

A const reference to m_T.

CAdapt::operator T&

Returns a reference to the m_T member, allowing the adapter object to be treated as if it were an object of type T.

operator T&();

Return Value

A reference to m_T.

CAdapt::operator <

Compares an object of the adapted type with m_T.

bool operator<(const T& rSrc) const;

Parameters

rSrc
A reference to the object to be compared.

Return Value

The result of the comparison between m_T and rSrc.

CAdapt::operator =

The assignment operator assigns the argument, rSrc, to the data member m_T and returns the current adapter object.

CAdapt& operator= (const T& rSrc);
CAdapt& operator= (T&& rSrCA); // (Visual Studio 2017)
CAdapt& operator= (CAdapt<T>&& rSrCA) noexcept; // (Visual Studio 2017)

Parameters

rSrc
A reference to an object of the adapted type to be copied.

rSrCA
A reference to an object to be moved.

Return Value

A reference to the current object.

CAdapt::operator ==

Compares an object of the adapted type with m_T.

bool operator== (const T& rSrc) const;

Parameters

rSrc
A reference to the object to be compared.

Return Value

The result of the comparison between m_T and rSrc.

See also

Class Overview