Nested QHash in range for loop

[Scope]

Thanks yeye_olive
Can you look on my implementation? I tested this code and think that it works fine.

class Container
{
public:
    Container();
 
    void setData(const Data &data);
 
 
    using value_type  = Data;
    using inner_range = QHash<QString, value_type>;
    using outer_range = QHash<QString, inner_range>;
 
    class iterator : std::iterator_traits<inner_range::iterator>
    {
    public:
        using iterator_category = std::forward_iterator_tag;
 
        iterator(outer_range::iterator const & outer_iterator,
                 outer_range::iterator const & outer_end)
            : outer_iterator(outer_iterator), outer_end(outer_end)
        {
            update();
        }
 
        iterator & operator++()
        {
            ++inner_iterator;
            if(inner_iterator == inner_end)
            {
                ++outer_iterator;
                update();
            }
            return *this;
        }
 
        value_type operator*() const
        {
            return *inner_iterator;
        }
 
        bool operator==(iterator const & rhs) const
        {
            bool lhs_end = outer_iterator == outer_end;
            bool rhs_end = rhs.outer_iterator == rhs.outer_end;
            if(lhs_end && rhs_end)
                return true;
            if(lhs_end != rhs_end)
                return false;
            return outer_iterator == rhs.outer_iterator
                && inner_iterator == rhs.inner_iterator;
        }
 
        bool operator!=(iterator const &other) const
        {
            return !(*this == other);
        }
 
 
    private:
        outer_range::iterator outer_iterator, outer_end;
        inner_range::iterator inner_iterator, inner_end;
 
        void update()
        {
            while(outer_iterator != outer_end)
            {
                inner_iterator = (*outer_iterator).begin();
                inner_end = (*outer_iterator).end();
                if(inner_iterator == inner_end)
                    ++outer_iterator;
                else
                    break;
            }
        }
    };
 
 
    Container::iterator begin();
    Container::iterator end();
 
private:
    QHash<QString, QHash<QString, Data>> d;
};

class Container
{
public:
    Container();

    void setData(const Data &data);


    using value_type  = Data;
    using inner_range = QHash<QString, value_type>;
    using outer_range = QHash<QString, inner_range>;

    class iterator : std::iterator_traits<inner_range::iterator>
    {
    public:
        using iterator_category = std::forward_iterator_tag;

        iterator(outer_range::iterator const & outer_iterator,
                 outer_range::iterator const & outer_end)
            : outer_iterator(outer_iterator), outer_end(outer_end)
        {
            update();
        }

        iterator & operator++()
        {
            ++inner_iterator;
            if(inner_iterator == inner_end)
            {
                ++outer_iterator;
                update();
            }
            return *this;
        }

        value_type operator*() const
        {
            return *inner_iterator;
        }

        bool operator==(iterator const & rhs) const
        {
            bool lhs_end = outer_iterator == outer_end;
            bool rhs_end = rhs.outer_iterator == rhs.outer_end;
            if(lhs_end && rhs_end)
                return true;
            if(lhs_end != rhs_end)
                return false;
            return outer_iterator == rhs.outer_iterator
                && inner_iterator == rhs.inner_iterator;
        }

        bool operator!=(iterator const &other) const
        {
            return !(*this == other);
        }


    private:
        outer_range::iterator outer_iterator, outer_end;
        inner_range::iterator inner_iterator, inner_end;

        void update()
        {
            while(outer_iterator != outer_end)
            {
                inner_iterator = (*outer_iterator).begin();
                inner_end = (*outer_iterator).end();
                if(inner_iterator == inner_end)
                    ++outer_iterator;
                else
                    break;
            }
        }
    };


    Container::iterator begin();
    Container::iterator end();

private:
    QHash<QString, QHash<QString, Data>> d;
};

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anda_skoa

And be aware that using a ranged for on a Qt container will require the Qt container to do a deep copy if it is used in more than one variable at the time of iteration.

What exactly you mean?
When I use this container like that:

for( const Data &x : d )
        qDebug()<< x.scope << "::" << x.name << ", " << x.value;

for( const Data &x : d )
        qDebug()<< x.scope << "::" << x.name << ", " << x.value;

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then it should not create a copy of each elemenet.

And importan question, whether i should stay with QHash whether I can obtain better performance using QMap?

Especially when keys are type of QString which can have between one to over a dozen characters and when each Container should have average 1 <= x <= 30 properties as Data.