This is a factory pattern written in just a few lines of code.
template <class ReturnType, class ...Args>
using Factory = std::function<ReturnType(Args...)>;Basically a Factory is a std::function that has a target callable that's based on parameters/arguments you define. This target callable will return an object of type ReturnType defined for the Factory.
An example of how to create a factory for a vector of N Animals:
/**
* This factory type must return a vector of Animal objects.
*/
using FarmFactory = factory::Factory<std::vector<Animal>>;
FarmFactory farmFactory(int N)
{
return [=]
{
std::vector<Animal> ret;
for (std::size_t i = 0; i < N; i++)
ret.push_back(Animal());
return ret;
};
}
// Create a farm with 20 animals
auto mediumFarmFactory = animalfactory::farmFactory(20); // Set the target based on parameters.
auto animals = mediumFarmFactory(); // Call the target of the std::function