container questions and probems.

[Jonas Wingren]

Hi!
I'm quite green so I might have formulated the question wrong.
I'm using a Class called "Cell" to save all the information i need to have about one cell on the map. However a map consists of 250k Cells and therefor I needed a way to create them.

I solved it by making this line of code:

const int NUM_CELLS = 250000;
Cell cellMap[NUM_CELLS];

The problem is that the functions used to get/set the Cells don't work unless I declare it in the global (scope?). Therefor I tried to make a class called Map that holds a vector that can contain the Cells. This is my attempt:

class Map
{
      public:
             Map(int spaces = 1) { m_Cells.reserve(spaces); }
             void Create();
             void Save();
             void Load();
             
             
      private:
              vector<Cell> m_Cells;

It won't compile since it forbids declaration of a vector object without a type. However in the example I am using as a reference I can't find the difference.




Example:(from beginning C++ game programming chapter 9)

//Critter Farm
//Demonstrates object containment

#include <iostream>
#include <string>
#include <vector>

using namespace std;

class Critter
{
public:

    Critter(const string& name = ""): m_Name(name) {}
    string GetName() const { return m_Name; }  
private:
    string m_Name;
};

class Farm
{
public:
    Farm(int spaces = 1) { m_Critters.reserve(spaces); }
    void Add(const Critter& aCritter) { m_Critters.push_back(aCritter); }
    void RollCall() const
    {
        for (vector<Critter>::const_iterator iter = m_Critters.begin(); 
             iter != m_Critters.end(); ++iter)
            cout << iter->GetName() << " here.\n";
    }
private:
    vector<Critter> m_Critters;
};

[wasabi]

Make sure you've declared Cell before you declared Map.

class Cell
{
//...
};
class Map
{
//...
}

Should work.

The compiler only knows what it's already read, so if you declare Map before declaring Cell, the compiler won't know what Cell is while trying to compile Map.

[Jonas Wingren]

Did that... still complains. Entire file:

/*The hexes contain functions to change the values of the variables available
buildings pop */
#include <iostream>
#include <vector>
using namespace std;
const int NUM_CELLS = 250000;

class Cell
{
          
      public:
             //constructor that requires (int, string) otherwise values as below
             Cell::Cell(int a = 1000, string b = "13212"){
             m_pop = a;
             m_buildings = b;
             }
      
             //static int s_Total = 0; //static data member
             //get and set
             int Getpop();
             string Getbuildings();
             void Setpop(int);
             void Setbuildings(string);
             // operations
             void Create();
             void Load();
             void Save();
      private:
              //data
              //*string m_powner;
              int m_pop;
              string m_buildings;
              };
              
class Map
{
      public:
             Map(int spaces = 1) { m_Cells.reserve(spaces); }
             void Create();
             void Save();
             void Load();
             
             
      private:
              vector<Cell> m_Cells;

[Jonas Wingren]

ah, had missed row 38 Map::Map
next problem... "Cell.cpp - cannot declare member function `Cell::Getpop' within `Map' "

suggestions?

[Jonas Wingren]

ok, solved almost all problems except that there seems to be a problem with this part:

vector<Cell>::const_iterator iter = m_Cells.begin(); 
          while(getline(Mapfile,line))
          {
                    stringstream(line) >> a;
                    iter->Setpop(a);
                    getline(Mapfile,line);
                    iter->Setbuildings(line);
                    ++iter;
          }

[Jonas Wingren]

ok, solved it all Thanks for the help!