MHO_ExtensibleElement.hh

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#ifndef MHO_ExtensibleElement_HH__
#define MHO_ExtensibleElement_HH__
 
#include <vector>
 
namespace hops
{
 
//forward declare these types
class MHO_Visitor;
class MHO_Element;
class MHO_ExtensibleElement;
template< class XExtensionType > class MHO_ExtendedElement;
 
//visitor interface
class MHO_Visitor
{
    public:
        MHO_Visitor(){};
        virtual ~MHO_Visitor(){};
};
 
class MHO_Element
{
    public:
        MHO_Element(){};
        virtual ~MHO_Element(){};
 
        virtual void Accept(MHO_Visitor* aVisitor) = 0;
};
 
class MHO_ExtensibleElement: public MHO_Element
{
    public:
        MHO_ExtensibleElement(){};
 
        virtual ~MHO_ExtensibleElement()
        {
            for(auto it = fExtensions.begin(); it != fExtensions.end(); it++)
            {
                delete (*it);
                (*it) = nullptr;
            }
            fExtensions.clear();
        }
 
        void Accept(MHO_Visitor* aVisitor) override
        {
            //the MHO_ExtensibleElement class by-itself is just a container,
            //no need to visit it by itself, just visit all the extentions
            for(auto it = fExtensions.begin(); it != fExtensions.end(); it++)
            {
                (*it)->Accept(aVisitor);
            }
        }
 
    public:
        template< class XExtensionType > bool HasExtension() const;
        template< class XExtensionType > MHO_ExtendedElement< XExtensionType >* MakeExtension();
        template< class XExtensionType > MHO_ExtendedElement< XExtensionType >* AsExtension();
 
    protected:
        std::vector< MHO_Element* > fExtensions;
};
 
 
template< class XExtensionType > inline bool MHO_ExtensibleElement::HasExtension() const
{
    MHO_ExtendedElement< XExtensionType >* extention;
    for(auto it = fExtensions.begin(); it != fExtensions.end(); it++)
    {
        extention = dynamic_cast< MHO_ExtendedElement< XExtensionType >* >(*it);
        if(extention != nullptr)
        {
            return true;
        }
    }
    return false;
}
 
template< class XExtensionType > inline MHO_ExtendedElement< XExtensionType >* MHO_ExtensibleElement::MakeExtension()
{
    MHO_ExtendedElement< XExtensionType >* extention;
    for(auto it = fExtensions.begin(); it != fExtensions.end(); it++)
    {
        extention = dynamic_cast< MHO_ExtendedElement< XExtensionType >* >(*it);
        if(extention != nullptr)
        {
            delete extention;
            fExtensions.erase(it);
            break;
        }
    }
    extention = new MHO_ExtendedElement< XExtensionType >(this);
    fExtensions.push_back(extention);
    return extention;
}
 
template< class XExtensionType > inline MHO_ExtendedElement< XExtensionType >* MHO_ExtensibleElement::AsExtension()
{
    MHO_ExtendedElement< XExtensionType >* extention;
    for(auto it = fExtensions.begin(); it != fExtensions.end(); it++)
    {
        extention = dynamic_cast< MHO_ExtendedElement< XExtensionType >* >(*it);
        if(extention != nullptr)
        {
            return extention;
        };
    }
    return nullptr;
}
 
 
template< class XExtensionType > class MHO_ExtendedElement: public MHO_Element, public XExtensionType
{
    public:
        MHO_ExtendedElement(MHO_ExtensibleElement* parent): XExtensionType(parent), fParent(parent){};
 
        virtual ~MHO_ExtendedElement(){};
 
    public:
        class ExtendedVisitor: public MHO_Visitor
        {
            public:
                ExtendedVisitor(){};
                virtual ~ExtendedVisitor(){};
 
                virtual void VisitExtendedElement(MHO_ExtendedElement< XExtensionType >* anElement) = 0;
        };
 
    public:
        virtual void Accept(MHO_Visitor* aVisitor) override
        {
            //visit this extension
            auto* extVisitor = dynamic_cast< typename MHO_ExtendedElement< XExtensionType >::ExtendedVisitor* >(aVisitor);
            if(extVisitor != nullptr)
            {
                extVisitor->VisitExtendedElement(this);
            };
        }
 
    protected:
        MHO_ExtensibleElement* fParent;
};
 
} // namespace hops
 
#endif