Description

This mixin merges the implementation of one interface with a second interface. Multiple inheritance from interfaces is not possible due to ambiguities. This mixin resolves the ambiguities by re-implementing the methods of mi::base::IInterface.

Note that this mixin class derives from an implementation and an interface, in contrast to mi::base::Interface_implement_2, which derives from two interfaces. Basically, Interface_merger<Interface_implement<I1>,I2> is equivalent to Interface_implement<I1,I2>. The benefit of this mixin class is that you are not bound to use Interface_implement, any valid implementation of an interface will do.

The template parameters representing the base classes are called MAJOR and MINOR. Note that the derivation is not symmetric:

• MAJOR has to be an implementation of an interface, MINOR has to be just an interface

• retain() and release() are redirected to the MAJOR base class

• compared_iid() and get_interface() are redirected to the MAJOR base class first, the MINOR base class is only queried on failure. For example, get_interface< mi::base::IInterface>() will always return the MAJOR base class.

• get_iid() is redirected to the MAJOR base class.

Note that some versions of Microsoft Visual C++ are known to produce the bogus warning

‎ disable C4505: <class::method>: unreferenced local function has been removed 

in conjunction with this class. This warning can be disabled with

‎ #include <mi/base/config.h>
 #ifdef MI_COMPILER_MSC
 #pragma warning( disable : 4505 )
 #endif

Note that the pragma affects the entire translation unit. Therefore, the warning is not disabled by default.