Static variables in template class results in smart enqueuer-dequeuer pattern.

Decorator pattern[1] tricks to reduce queue dependency

TL;DR this one simple trick for static member initialization in a class template[2].

The original rather dumb enqueuer and dequeuer used the shared_queue class to track their counts and close the underlying queue accordingly. Giving them each their own static count makes the shared_queue wrapper redundant and usage more intuitive, but how to initialise the static variable was a brief head scratcher...

Smart dequeuer decorator:

	namespace que {
	template<typename T>
	class dequeuer final {
	using value_type = typename T::value_type;
	public:
	dequeuer(T& q): q(q) {
	count++;
	}
	value_type dequeue() {
	return q.dequeue();
	}
	bool try_dequeue(value_type& item) {
	return q.dequeue(item);
	}
	inline bool is_open() {
	return q.is_open();
	}
	~dequeuer() {
	if (!--count)
	q.close();
	}
	private:
	T& q;
	static unsigned int count;
	};
	//this one simple trick for static member initialization in a class template
	template<typename T>
	unsigned int dequeuer<T>::count = 0;
	}

view raw dequeuer.cpp hosted with ❤ by GitHub

References:
[1] http://en.wikipedia.org/wiki/Decorator_pattern
[2] static member initialization in a class template