| Author: | F.Mauger <[email protected]> |
|---|---|
| Date: | 2020-03-18 |
This header-only C++ library provides somes classes and macros to easily implement factories of objects.
User classes are registered in some local or global (singleton) register objects using an unique registration string identifier. Client code can request such a register to instantiate default constructed objects of any registered class on-the-fly. Registered factories create objects addressed by pointers. It is the responsability of the client code to manager such a pointer, typically through a smart pointer. Configuration/initialization of the created objects is also under the responsibility of the client code.
A class addressed by the factory registration mechanism implemented in BxFactories must :
- inherit some unique base class, possibly abstract (interface and polymorphism),
- have a default constructor which preferably instantiates objects of this class in some reasonable state, meaning the object is not necessarily immediately usable after creation but at least is not corrupted or malformed (no uninitialized pointer member...), which should be the case in any circonstances anyway,
- be associated by the user or the developper to some unique string
identifier (here unique means the user/developper must carefully
choose this identifier to avoid name collision, particularly when
classes are registered in the same factory register from various
compilation units. It is recommended to use a stringification of
the full class C++ identifier like
"foo::bar::my_class").
BxFactories is inspired by some work from the Bayeux library. I do not expect its approach works in all contexts where object factories are needed. It has worked for years in various of my projects. I would be happy if it is also useful within other people's projects.
BxFactories use the C++11 standard and depends on the Boost library (header only). I guess this dependency could be removed soon using C++11 features (TODO).
Albeit BxFactories may use global singleton factory registers, each associated to a base class of user choice and automatically populated thanks to preprocessing macros, it is not mandatory to use this technique. You may create your own factory register and fill it with some specific set of object factories of your choice. In such a case, you are responsible of managing the factory register object by yourself.
Example 1 in the examples directory illustrates some possible
usage of BxFactories.