在“掌握C++17 STL”一书中，我看到iterator和const_iterator在一个类中实现，使用条件来减少代码重复

下面是我对简单数组类的实现（跳过数组类的大部分代码）：

template<class T, size_t N>
class Array
{
public:
    template<bool Const>
    class ArrayIterator {
        friend class Array;
    public:
        using difference_type = std::ptrdiff_t;
        using value_type = T;
        using pointer = std::conditional<Const, const value_type*, value_type*>;
        using reference = std::conditional<Const, const value_type&, value_type&>;
        using iterator_category = std::random_access_iterator_tag;

        reference operator*() const { return *ptr; }
        ArrayIterator<Const>& operator++() { ++ptr; return *this; }
        ArrayIterator<Const> operator++(int) { auto res = *this; ++(*this); return res; }

        template<bool R>
        bool operator==(const ArrayIterator<R>& iter) const { return ptr == iter.ptr; }
        template<bool R>
        bool operator!=(const ArrayIterator<R>& iter) const { return ptr != iter.ptr; }

    private:
        explicit ArrayIterator(pointer p) : ptr(p) {};
        pointer ptr;
    };

    using iterator = ArrayIterator<false>;
    using const_iterator = ArrayIterator<true>;
    iterator begin() { return iterator(data); }
    iterator end() { return iterator(data + N); }
    const_iterator cbegin() const { return const_iterator(data); }
    const_iterator cend() const { return const_iterator(data + N); }

private:
    T* data;
};

这段代码编译时没有错误,但iterator有点不可用：

Array<int, 100> arr;
/*filling it with numbers*/
int x = *arr.begin(); 

给出错误：

main.cpp:9:9: error: no viable conversion from 'Array<int, 100>::ArrayIterator<false>::reference' (aka 'conditional<false, const int &, int &>') to 'int'

我该如何使用那个迭代器呢？还是我应该从书上放弃这个想法呢？