access_observer.h

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#ifndef DD_ACCESS_OBSERVER_INTERFACE_H_INCLUDED
#define DD_ACCESS_OBSERVER_INTERFACE_H_INCLUDED
 
#include <string>
#include <vector>
 
namespace ddl {
 
namespace dd {
 
namespace utility {

template <typename MODEL_SUBJECT_T, typename EVENT_CODE_T>
class ModelObserverUtility {
public:
    typedef EVENT_CODE_T event_code_type;
    typedef MODEL_SUBJECT_T subject_type;
 
protected:
    virtual ~ModelObserverUtility(){};
 
public:
    virtual void modelChanged(event_code_type event_code,
                              subject_type& changed_subject,
                              const std::string& additional_info) = 0;
};

template <typename MODEL_SUBJECT_T, typename EVENT_CODE_T>
class ModelSubjectUtility {
public:
    typedef EVENT_CODE_T event_code_type;
    typedef MODEL_SUBJECT_T subject_type;
    typedef ModelObserverUtility<MODEL_SUBJECT_T, EVENT_CODE_T> observer_type;
    ModelSubjectUtility() = default;
    ModelSubjectUtility(const ModelSubjectUtility&)
    {
        // nothing to do
        // copy means we erase the current observers so we do not copy it
    }

    ModelSubjectUtility& operator=(const ModelSubjectUtility&)
    {
        // nothing to do
        // copy means we erase the current observers so we do not copy it
        return *this;
    }

    virtual ~ModelSubjectUtility() = default;

    void attachObserver(observer_type* observer)
    {
        for (auto& current: _observers) {
            if (current == observer) {
                return;
            }
        }
        _observers.push_back(observer);
    }

    void detachObserver(observer_type* observer)
    {
        for (auto current = _observers.begin(); current != _observers.end(); ++current) {
            if (*current == observer) {
                _observers.erase(current);
                return;
            }
        }
    }
 
protected:
    void notifyChanged(event_code_type event_code,
                       subject_type& changed_subject,
                       const std::string& additional_info)
    {
        // we take a copy, to prevent invalidation of the iterator
        auto observers_copy = _observers;
        for (auto& current: observers_copy) {
            current->modelChanged(event_code, changed_subject, additional_info);
        }
    }
 
private:
    std::vector<observer_type*> _observers;
};
 
} // namespace utility
} // namespace dd
namespace utility {
    using dd::utility::ModelSubjectUtility;
    using dd::utility::ModelObserverUtility;
}
} // namespace ddl
 
#endif // DD_ACCESS_OBSERVER_INTERFACE_H_INCLUDED