Active Template Library
The Active Template Library (ATL) is a set of template-based C++ classes developed by Microsoft, intended to simplify the programming of Component Object Model (COM) objects. The COM support in Microsoft Visual C++ allows developers to create a variety of COM objects, OLE Automation servers, and ActiveX controls. ATL includes an object wizard that sets up primary structure of the objects quickly with a minimum of hand coding. On the COM client side ATL provides smart pointers that deal with COM reference counting. The library makes heavy use of the curiously recurring template pattern.
|Operating system||Microsoft Windows|
|Type||Library or framework|
COM objects can also be created with Microsoft Foundation Classes (MFC), but this leads to larger binaries that require support DLLs. ATL, on the other hand, is a more lightweight alternative in situations where the graphical user interface parts of MFC are not required.
In ATL version 7 (Visual Studio 2003), which directly succeeded version 3 (Visual Studio 6.0), a number of MFC classes like CString were made available in ATL, or more precisely moved to an ATLMFC common layer which is shared by both libraries. ATL version 7 also introduced attributes in C++ in an attempt to provide something similar to CLI attributes, however these have not been particularly successful, and have been deemphasized in ATL version 8 (Visual Studio 2005); the various wizards no longer generate them by default. Version 7 also introduced new string conversion classes.
Since Visual Studio 2013, ATL code in Visual C++ 2013 is static, eliminating the DLL.
ATL includes many RAII classes to simplify management of COM types. The most commonly used classes include:
Compiler COM supportEdit
Although not formally part of ATL, Microsoft Visual C++ also includes additional C++ RAII classes to simplify management of COM types. These compiler COM support classes can be used as replacement for or in combination with ATL, and includes:
_com_ptr_t smart-pointer that decorates the COM interface name with a "Ptr" suffix,
_bstr_t BSTR wrapper,
_variant_t VARIANT wrapper, and
_com_error HRESULT wrapper.
Note that as of Visual Studio 2012, the compiler COM support classes does not include a SAFEARRAY wrapper.
- Grimes, Richard (1998). "ATL and COM". ATL COM (1st ed.). Wrox Press. p. 6. ISBN 1-86100-249-1.
- Grimes, Richard (1999). "Building and calling a COM object using ATL". Beginning ATL 3 COM Programming (1st ed.). Wrox Press. p. 63. ISBN 978-1-86100-120-7.
- Williams, Mickey (2000). "Active Documents". Visual C++ 6 Unleashed (1st ed.). Sams. p. 733. ISBN 978-0-672-31241-0.
- Microsoft MSDN: Recommendations for Choosing Between ATL and MFC
- "ATL Security Update". MSDN. Microsoft. 2009-07-28. Retrieved 2011-09-19.
- ATL and MFC changes and fixes in Visual Studio 2013 http://blogs.msdn.com/b/vcblog/archive/2013/08/20/atl-and-mfc-changes-and-fixes-in-visual-studio-2013.aspx
- Microsoft MSDN: CComPtr Class
- Microsoft MSDN: CComBSTR Class
- Microsoft MSDN: CComVariant Class
- Microsoft MSDN: CComSafeArray Class
- Microsoft MSDN: _com_ptr_t Class
- Microsoft MSDN: _bstr_t Class
- Microsoft MSDN: _variant_t Class
- Microsoft MSDN: _com_error Class