const problem... can't find it

[maroun]

Hey all,

The error is:

Error 1 error C2678: binary '=' : no operator found which takes a left-hand operand of type 'const std::string' (or there is no acceptable conversion).

Code:

classes :

class Coogle
{
private:
vector<map<string,unsigned int>> map_vec ;
public:
Coogle(const string s);
~Coogle();

int getNumOfWords() const;
void loadFile(const string filename);

};

class new_map_vec
{

private:

map<string,unsigned int> merge_map;

public:

void merge_maps(vector<map<string,unsigned int>> map_vec);
void get_map(map<string,unsigned int> &user_map);
new_map_vec();
~new_map_vec();
};

The problem accured when I started using these functions:

void new_map_vec::get_map(map<string,unsigned int> &user_map)
{
copy(merge_map.begin(),merge_map.end(),user_map.begin());
};


int Coogle::getNumOfWords() const
{
new_map_vec map_cont;
int count=0;
map<string,unsigned int> temp;
map<string,unsigned int>::iterator iter;
map_cont.get_map(temp);

for(iter=temp.begin();iter!=temp.end();iter++)
count++;

return count;
};

why is that happening ?? please help
Thank you !!

[ne555]

The map's iterators are constant.
You could try to use an inserter http://www.cplusplus.com/reference/std/iterator/inserter/
or just review your design...

new_map_vec map_cont;
map<string,unsigned int> temp;
map_cont.get_map(temp);

I suppose that that will have no effect

[vlad from moscow]

The value_type for std::map is defined the following way

typedef pair<const Key, T> value_type

So you can not assign one object of the value_type to another object.

[maroun]

sorry ne555, but I didn't understand what u said :(

vlad what should I do, merge_map is private and I need to use it in another class function... so I wrote the get_map function.
send iterator to function ?

[ne555]

The key is used to construct the map, so you can't happily change it.

I don't understand what you are trying to accomplish. For what matters, your map is empty when you call that function.

vector<map<string,unsigned int> > new_map_vec::get_a_copy_of_my_guts() const{
   return merge_map;
}

void new_map_vec::unite_the_kingdom( const vector<map<string,unsigned int> > &m ){
   merge_map.insert( m.begin(), m.end() );
}

Tell what you want to do, not how you are doing it (because you are doing it wrong)