Subject.hh

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#ifndef SUBJECT_HH
#define SUBJECT_HH

#include "Observer.hh"
#include "ScopedAssign.hh"
#include <algorithm>
#include <vector>
#include <cassert>

namespace openmsx {

template <typename T> class Subject
{
public:
        void attach(Observer<T>& observer);
        void detach(Observer<T>& observer);

protected:
        Subject();
        ~Subject();
        void notify() const;

private:
        std::vector<Observer<T>*> observers;
#ifndef NDEBUG
        mutable bool notifyInProgress;
#endif
};

template <typename T> Subject<T>::Subject()
#ifndef NDEBUG
        : notifyInProgress(false)
#endif
{
}

template <typename T> Subject<T>::~Subject()
{
        assert(!notifyInProgress);
        auto copy = observers;
        for (auto& o : copy) {
                o->subjectDeleted(*static_cast<const T*>(this));
        }
        assert(observers.empty());
}

template <typename T> void Subject<T>::attach(Observer<T>& observer)
{
        assert(!notifyInProgress);
        observers.push_back(&observer);
}

template <typename T> void Subject<T>::detach(Observer<T>& observer)
{
        assert(!notifyInProgress);
        auto it = find(observers.begin(), observers.end(), &observer);
        assert(it != observers.end());
        observers.erase(it);
}

template <typename T> void Subject<T>::notify() const
{
#ifndef NDEBUG
        assert(!notifyInProgress);
        ScopedAssign<bool> sa(notifyInProgress, true);
#endif

        for (auto& o : observers) {
                o->update(*static_cast<const T*>(this));
        }
}

} // namespace openmsx

#endif