Sparkx Embedded Maps
May 18th, 2009
object_factory
May 17th, 2009
For some reason, I needed a object factory. Well, that’s easy you might think: this subject is well understood and textbook material.
It turns out differently.
There are in fact several places where you can look: - Loki - Codeproject - Boost Sandbox
But these are all either too specialized or too generalized: nothing fitted quite what I needed: an object factory that creates objecst based on the types of the constructor parameters …
For example:
typedef ObjectFactory<base* (int, float), short> factory_t; |
where base* (int, float) is the constructor signature, and short is the key (but you could use std::string just as easily).
The best solution was to be found on Gamedev
But this too needed a bit of attention: I wanted N constructor parameters, without having to specialize them by hand – as that would be silly.
So, with the help of Boost.Preprocessor I came up with the following.
The template is here
The template is specialized once for a constructor without arguments, and with the use of Boost.Preprocessor N times; well, between LIMIT_LOWER_BOUND and LIMIT_UPPER_BOUND – which you can adjust if you need more …
The above will allow for code like this unit-test
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struct base {}; struct node1 : public base { node1(int) { std::cout << "node1(int)" << std::endl; } node1(int, float) { std::cout <<"node1(int, float)" << std::endl; } }; void test_object_factory() { std::wcout << L"object_factory_test: " << std::endl; typedef ObjectFactory<base* (int, float), char*> node1_factory_t; node1_factory_t nf; nf.Register<node1>("node1"); base* n1 = nf.Create("node1", 2, 3.0); delete n1; |
This would create an object with the (int, float) signature.