NullReferenceException on push_back

Question

I am getting a nullReferenceException when using vector.push_back on a new object.

In the code segment you see I have the vector object as a pointer but I originally had it as a non-pointer, I changed it in my troubleshooting out of desperation.

I stepped through the instantiation of BasicSolver completely to make sure the were no issues in it and also separated the instantiation from the push_back to help show that push_back is where the problem is occurring.

InformedSolver1&2 are children of BasicSolver. vector is included in BasicSolver and therefore in puzzleSolver also.

#include "stdafx.h"
#include "puzzleSolver.h"


PuzzleSolver::PuzzleSolver()
{
   solvers = new vector<BasicSolver*>();
}

void PuzzleSolver::createPuzzle(string input)
{                                             //hitting step-over
   BasicSolver* temp = new BasicSolver(input);// no errors
   solvers->push_back(temp);                  // nullReferenceException
   solvers->push_back(new InformedSolver1(input));
   solvers->push_back(new InformedSolver2(input));
}

That should be all the relevant information. Let me know if you have any ideas as to what is causing this/ how to fix it! Thanks.

Edit: Added BasicSolver constuctor and dependency methods by comment request also a little background: this is a Sudoku solver for an AI class

BasicSolver::BasicSolver(string input)
{
   peers = new vector<Peer*>();
   squares = new vector<Square*>();
   unsolved = new vector<Square*>();
   solved = new vector<Square*>();
   createStructure(input);
   original = input;
   mistakes = 0;
}

void BasicSolver::createStructure(string input)
{
   try
   {
       createEmptyStructure(peers, squares, unsolved);
      //Parse the puzzle and assign input to squares
      int numCharsToRead = MAX_SQUARES;   //makes sure vector isn't outside its range
      if (input.length() < MAX_SQUARES)   //makes sure string isn't outside its range
         numCharsToRead = input.length(); 
      for (int i = 0; i < numCharsToRead; i++)
      {
         if(input[i] != '.')
            insertValue(input[i], (*squares)[i], unsolved);
      }
   }
   catch(exception e)
   {
      throw e;
   }
}

void BasicSolver::createEmptyStructure(vector<Peer*> *workingPeers, vector<Square*> *workingSquares, vector<Square*> *workingUnsolved)
{
    for (int i = 0; i < MAX_PEERS; i++)
    {
        workingPeers->push_back(new Peer());
    }
   for (int i = 0; i < 81; i++)
   {
      try
      {
          workingSquares->push_back(new Square('.'));

         //Adding the square to its corresponding peers
         (*workingPeers)[i / MAX_ROWS]->addSquare((*workingSquares)[i]); //adds the square into its appropriate row of peers
         (*workingPeers)[(i % MAX_ROWS) + COL_OFFSET]->addSquare((*workingSquares)[i]); //adds the square into its appropriate column of peers
         int tempBoxCol = (i % MAX_ROWS) / MAX_BOX_COLS; //returns the box column (0,1,2)

         if ((i / MAX_ROWS) < BOX_ROW_WIDTH) //if its box is in the first row
         {
             (*workingPeers)[tempBoxCol + BOX_OFFSET]->addSquare((*workingSquares)[i]);
         }
         else if ((i / MAX_ROWS) < (2 * BOX_ROW_WIDTH)) //if its box is in the second row
         {
             (*workingPeers)[BOX_ROW_WIDTH + tempBoxCol + BOX_OFFSET]->addSquare((*workingSquares)[i]);
         }
         else //if the box is in the third row
         {
             (*workingPeers)[2 * BOX_ROW_WIDTH + tempBoxCol + BOX_OFFSET]->addSquare((*workingSquares)[i]);
         }
      }
      catch(exception e)
      {
         throw e;
      }
   }
   *workingUnsolved = *workingSquares;
}

Edit2: Personal tests add these lines:

vector<BasicSolver*>* test = new vector<BasicSolver*>();
test->push_back(temp);

before

solvers->push_back(temp);

and they execute fine, I also notice that during runtime solvers is listed as outside of scope even though it is a protected variable of BasicSolver.

Answer 1

The problem was that the calling source did not have PuzzleSolver properly instantiated. Thanks to @TheDark for suggesting I check that!