A problem with vectors

Im not sure if I should be posting this here or the game programming forum.

Anyway...the deal is... I am using vectors instead of arrays to track PLAYER potions.

here is the code...I commented where the problems lie...there is over 400 lines of code so I am only going to post snippets.


Top of Town.cpp where I declared the vector and its iterator.

Code:

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#include "Library.h"
#include "Globals.h"

using std::cin;
using std::cout;
using std::endl;

// I am not too sure of where to declare this vector
std::vector<POTION>potions(15);
std::vector<POTION>::iterator i;

void Armory(PLAYER*);
void ItemShop(PLAYER*);

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ItemShop function

Code:

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void ItemShop(PLAYER* player)
{
    cout << "As you step inside, a pleasant smell wafts up to your nose.  You see\n"
          << "a kindly heavyset older woman watering plants, that decorate the shop.\n" << endl;
    Pause();
    cout << "What would you like to do?\n"
          << "<1> Talk to the woman.\n"
          << "<2> Exit\n"
          << ">";
    int answer = -1;
    cin  >> answer;
    cin.clear();
    cin.ignore(INT_MAX,'\n');
   
    if (answer == 1)
    {
        cout << "Hello Traveler!  Welcome to Suzies Pots and Herbs.\n"
              << "How may I help you?\n" << endl;
        Pause();
        Clr_Scrn();
       
        bool shoploop = true;

        while (shoploop = true)
        {
        cout << "What do you want to do?\n"
              << "<1> Buy Potions\n"
              << "<2> Buy Spells\n"
              << "<3> View Stats\n"
              << "<4> Exit\n"
              << ">";
        int choice = -1;
        cin  >> choice;
        cin.clear();
        cin.ignore(INT_MAX,'\n');
       
        switch(choice)
        {
              case 1:
                  {
                      POTION* potionlist = new POTION[7];
                      potionlist[0].CreatePotion("Small Health Potion", 10, 30, 50);
                      potionlist[1].CreatePotion("Medium Health Potion", 30, 100, 100);
                      potionlist[2].CreatePotion("Large Health Potion", 100, 300, 1000);
                      potionlist[3].CreatePotion("Elixer", 9999, 9999, 10000);
                      potionlist[4].CreatePotion("Small Mana Potion", 10, 50, 100);
                      potionlist[5].CreatePotion("Medium Mana Potion", 30, 100, 100);
                      potionlist[6].CreatePotion("Large Mana Potion", 100, 300, 1000);
                     
                      cout << "Name: " << "Restore: " << "Price: " << endl;
                      for (int loop = 0; loop < 6; loop++)
                      {
                          cout << loop + 1 << potionlist[loop].GetName() << " " <<
                          potionlist[loop].GetMinRestore() << "-" << potionlist[loop].GetMaxRestore()
                          << potionlist[loop].GetPrice() << endl;
                          }
                      cout << "0: Exit\n"
                            << "What do you want to buy?\n";
                      int decision = -1;
                      cin  >> decision;
                      cin.clear();
                      cin.ignore(INT_MAX,'\n');
                     
                      if (decision > 0 && decision < 8)
                      {
                            if (player->GetGold() >= potionlist[decision-1].GetPrice())
                            {
                                  player->SpendGold(potionlist[decision-1].GetPrice());
                                 
                                  // places potion in vector
                                  potions.push_back(potionlist[decision-1]);
                                 
                                  // this is only to test to see the capacity of the vector
                                  // for some reason it outputs 30--when should be 15
                                  cout << endl << potions.capacity() << endl;
                                 
                                  // to test how much memory is inialized inside the vector
                                  // which for some reason outputs 16--when should be 1
                                  cout << potions.size() << endl << endl;
                                 
                                  // put this in just to see what the heck was going on and am now
                                  // more confused than ever!!!!
                                  // first 15 outputs is dobldegook
                                  // the 16th is the potion that you actually bought!!!
                                  for(i = potions.begin(); i != potions.end(); ++i)
                                  {
                                        cout << i->GetName() << endl;
                                        }
                                 
                                  cout << "You have purchased a " << potionlist[decision-1].GetName()
                                  << endl;
                                  cout << "Do you want to make another purchase? 1 for yes 2 for no\n";
                                  cin  >> shoploop;
                                  cin.clear();
                                  cin.ignore(INT_MAX,'\n');
                                  Clr_Scrn();
                                  delete [] potionlist;
                                  break;
                                  }
                            else
                            {
                                  cout << "You cant afford this!!\n" << endl;
                                  Pause();
                                  Clr_Scrn();
                                  delete [] potionlist;
                                  shoploop = true;
                                  break;
                                  }
                                  }
                      else if (decision == 0)
                      {
                            delete [] potionlist;
                            shoploop = false;
                            break;
                            }
                      else
                      cout << "Invalid Selection" << endl;
                      shoploop = true;
                      Pause();
                      Clr_Scrn();
                      break;
                      }

---

> potionlist[6].CreatePotion("Large Mana Potion", 100, 300, 1000);
Well this is off the end of your allocated memory, so fix that first.

ouch...I did that with all of my dynamic arrays:(

Code:

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std::vector<POTION>potions(15);

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That code creates a vector with 15 elements (meaning size() is 15). The capacity can be anything 15 or higher. When you use push_back later, you are adding an element so the size is then 16. The capacity won't change after push_back unless it is too small to hold one more element.

If you want to start with an empty vector and use push_back, create it with this:

Code:

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std::vector<POTION>potions;

---

Or, you can create it like you did originally and just not use push_back.

BTW, the reason "dobldegook" is output for the first 15 is that they are default initialized. If your POTION class or struct does not have a constructor to initialize its members, then they may contain uninitialized values.

Okay....that makes sense

The reason I did that way was because I dont want the vector to exceed 15 items.

I guess I could do it this way then

Code:

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if (potions.size() == 15)
{
      cout << "Your inventory is already full!" << endl;
}

---

or something like that

>// I am not too sure of where to declare this vector
>std::vector<POTION>potions(15);
push_back creates a new element, so you don't need to create 15 elements here, unless you use something like:

Code:

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potions[count] = potionlist[decision-1];

---

to store the new potion. Instead you can just use:

Code:

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std::vector<POTION> potions;

---

As far as where to declare it, if you made a class you could declare it in the class. Otherwise in main(), and you'd pass this vector to any function which needed it.

yeah I thought about declaring it in the class, but wasnt sure about how to do it...
passing the vector to a functions sounds much easier.

this is my first time working with vectors...

Code:

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// I am not too sure of where to declare this vector
std::vector<POTION>potions(15);

---

Declare the vector where it makes sense. Perhaps you could create a WORLD* structure or something and pass it to your functions along with the PLAYER*.

Code:

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cin.ignore(INT_MAX,'\n');

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Perhaps this would be a better idea:

Code:

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cin.ignore(std::numeric_limits<std::streamsize>::max(),'\n');

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I can't remember if it's streamsize, streambuf, or one of those with an underscore in it. :)

Quote:

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Perhaps this would be a better idea:
Code:

cin.ignore(std::numeric_limits<std::streamsize>::m ax(),'\n');

I can't remember if it's streamsize, streambuf, or one of those with an underscore in it.

---

That works..

What is the difference between the two?

Well, the std::streamsize code is better because that's the actual data type that is used. INT_MAX is usually what std::numeric_limits<std::streamsize>::max() is set to, but not always. See here for a better description: http://cboard.cprogramming.com/showthread.php?t=82416

Oh yes, and apparently (I had forgotten this) streamsize is in <ios>:

Code:

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#include <ios>      // For streamsize

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http://cboard.cprogramming.com/showthread.php?t=85987

But even using INT_MAX is great. Most people just use 9999 or something. :)

Code:

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while (shoploop = true)

---

Typo?

no...its my error ridden shoploop thingamajig:) ....I have been meaning to change it for a while.