Question

Hi can anyone tell me why VS2010 gives me an error with this code, I can’t see what’s the problem with it?

Error code : error C2679: binary ‘=’ : no operator found which takes a right-hand operand of type ‘std::vector<_Ty>’ (or there is no acceptable conversion)

// Elements container
typedef std::vector<CFVFElementPtr> ElementArray;
typedef std::map<CVertexSemantic::Type, ElementArray> ElementsMap;

// Create an empty array of elements
ElementsMap::value_type::second_type allElements;

// Concatinate each std::vector found within the map
std::transform(m_elementsMap.begin(), m_elementsMap.end(),
std::insert_iterator<ElementArray>(allElements, allElements.end()),
select2nd<ElementsMap::value_type>() );

All I am trying to do is this

for (auto i = m_elementsMap.begin(); i != m_elementsMap.end(); ++i)
{
    const ElementArray& elements = (*i).second;
    allElements.insert(allElements.end(), elements.begin(), elements.end());
}

As a response to Pablo, I tried creating a custom iterator that accepts an array of ElementArray, but I’m now getting a bucket load of errors.

template < class Container >
class container_insert_interator
{
public:
    typedef container_insert_interator<Container> this_type;
    typedef Container container_type;
    typedef typename Container::const_reference const_reference;
    typedef typename Container::value_type valty;

    explicit container_insert_interator (Container& cont, typename   Container::iterator iter) 
            : container(&cont), iter(iter)
    { }

    this_type& operator = (typename const_reference value)
    { 
        iter = container->insert( iter, std::begin(value), std::end(value) );
        ++iter;
        return *this;
    }

    this_type& operator* ()
    { 
       return *this;
    }

    this_type& operator++ ()
    { 
           return *this;
    }

    this_type operator++ (int)
    {
       return *this;
    }

protected:
    Container* container; // pointer to container
    typename Container::iterator iter ; // iterator into container
};

Answer 1

The problem is ElementsMap::value_type::second_type is ElementArray. That is, you’re trying to insert instances of ElementArray into an ElementArray, which really holds instances of CFVFElementPtr.

Update: Changing your declaration of operator= from

this_type& operator = (typename const_reference value)

to

template<typename OtherContainer>
this_type& operator = ( OtherContainer const& value)

almost works. Except that neither VS 2010 or GCC 4.6.1 provide the vector::insert overload that returns an iterator. You’ll probably need a newer compiler if you want your ranged insert to return an iterator to replace iter.

Changing the implementation to always insert at the end, namely

container->insert( container->end(), std::begin(value), std::end(value) );

in operator= compiles fine with GCC 4.6.1 (and, of course, you can remove all references to iter in your iterator class).