Thread: problem with pointers

I am developing a simple personal finance program. In this program I have a class (CAccountViewer) that simply displays the transactions from a particular account and also allows to enter new transactions. I have another class (CAccountManager) that maintains a list of accounts in a std::map. When the user clicks on an account control transfers to CAccountViewer and the account viewer requests a pointer to the account that the user selected from CAccountManager and saves that pointer as a member variable. This all works fine but when the I attempt to add a new transaction I get a seg fault. Debbuging shows me that the address that the pointer points to becomes invalid somewhere but I can't figure out where. Here is the relivant code.

this is where the user selects an account to view :

Code:

void CHomeFrame::OnListBoxSelect(wxCommandEvent &event)
{
    int sel = m_pAccountListBox->GetSelection();
    if (sel != -1)
    {
        wxString AccountName = m_pAccountListBox->GetString(sel);
        m_StateManager.AddNewState(new CAccountViewer(this, &m_AccountManager, AccountName) );
    }
}

control then transfers to the account viewer here :

Code:

CAccountViewer::CAccountViewer(wxWindow *pParent, CAccountManager *pAM, wxString &AccountName)
: wxPanel(pParent, ID_DATAWINDOW)
{
    SetOwnBackgroundColour(wxColour(100, 100, 100) );
    m_Balance = 0.0;
    m_AccountNames = pAM->GetAccountNames();
    m_pAccount = pAM->GetAccount(AccountName);
    m_pGrid = new wxGrid(this, ID_DATAWINDOW, wxDefaultPosition, wxDefaultSize, wxVSCROLL);
    if (!m_pGrid->CreateGrid(0, 9) ) SHOWERROR("Could not create grid");
    m_pGrid->BeginBatch();
      m_pAccount->ResetTransactionCounter();
      while (m_pAccount->HasMoreTransactions() )
      {
          AddNewRow(m_pAccount->GetNextTransaction(), false);
      }
    m_pGrid->EndBatch();
    // set up the button panel
    m_pButtonPanel = new wxPanel(this, ID_BUTTONPANEL);
    m_pButtonPanel->SetBackgroundColour(wxColour(200, 200, 200) );
    // set up the buttons
    wxButton *pBtnCheck    = new wxButton(m_pButtonPanel, IDB_CHECK, wxT("Check") );
    wxButton *pBtnDebit    = new wxButton(m_pButtonPanel, IDB_DEBIT, wxT("Debit") );
    wxButton *pBtnDeposit  = new wxButton(m_pButtonPanel, IDB_DEPOSIT, wxT("Deposit") );
    wxButton *pBtnATM      = new wxButton(m_pButtonPanel, IDB_ATM, wxT("ATM") );
    wxButton *pBtnTransfer = new wxButton(m_pButtonPanel, IDB_TRANSFER, wxT("Transfer") );
    wxBoxSizer *pButtonSizer = new wxBoxSizer(wxVERTICAL);
    pButtonSizer->Add(new wxStaticText(m_pButtonPanel, wxID_ANY, wxT("Enter a new Transaction") ),
                      1,
                      wxALIGN_LEFT | wxALL, 3);
    pButtonSizer->Add(pBtnCheck, 1, wxALIGN_LEFT | wxALL, 3);
    pButtonSizer->Add(pBtnDebit, 1, wxALIGN_LEFT | wxALL, 3);
    pButtonSizer->Add(pBtnDeposit, 1, wxALIGN_LEFT | wxALL, 3);
    pButtonSizer->Add(pBtnATM, 1, wxALIGN_LEFT | wxALL, 3);
    pButtonSizer->Add(pBtnTransfer, 1, wxALIGN_LEFT | wxALL, 3);
    m_pButtonPanel->SetSizer(pButtonSizer);
    wxBoxSizer *pVSizer = new wxBoxSizer(wxVERTICAL);
    pVSizer->Add(m_pGrid, 4, wxALIGN_CENTER | wxALL | wxEXPAND, 5);
    pVSizer->Add(m_pButtonPanel, 1, wxALIGN_CENTER | wxALL | wxEXPAND, 5);
    SetSizer(pVSizer);
    // attach handlers
    // mouse right click on grid
    Connect(ID_DATAWINDOW, wxEVT_GRID_CELL_RIGHT_CLICK,
            wxGridEventHandler(CAccountViewer::OnTransactionRightClick) );
    // popup command menu from grid
    Connect(IDM_VIEW_TRANSACTION, wxEVT_COMMAND_MENU_SELECTED,
            wxCommandEventHandler(CAccountViewer::OnViewTransaction) );
    Connect(IDM_VIEW_IMAGES, wxEVT_COMMAND_MENU_SELECTED,
            wxCommandEventHandler(CAccountViewer::OnViewImages) );
    Connect(IDM_EDIT_TRANSACTION, wxEVT_COMMAND_MENU_SELECTED,
            wxCommandEventHandler(CAccountViewer::OnEditTransaction) );
    Connect(IDM_DELETE_TRANSACTION, wxEVT_COMMAND_MENU_SELECTED,
            wxCommandEventHandler(CAccountViewer::OnDeleteTransaction) );
    Connect(IDM_CHANGE_TRANSACTION_STATUS, wxEVT_COMMAND_MENU_SELECTED,
            wxCommandEventHandler(CAccountViewer::OnChangeTransactionStatus) );
    // buttons
    pBtnCheck->Connect(IDB_CHECK, wxEVT_COMMAND_BUTTON_CLICKED,
                       wxCommandEventHandler(CAccountViewer::OnNewTransaction) );
    pBtnDebit->Connect(IDB_DEBIT, wxEVT_COMMAND_BUTTON_CLICKED,
                       wxCommandEventHandler(CAccountViewer::OnNewTransaction) );
    pBtnDeposit->Connect(IDB_DEPOSIT, wxEVT_COMMAND_BUTTON_CLICKED,
                         wxCommandEventHandler(CAccountViewer::OnNewTransaction) );
    pBtnATM->Connect(IDB_ATM, wxEVT_COMMAND_BUTTON_CLICKED,
                     wxCommandEventHandler(CAccountViewer::OnNewTransaction) );
    pBtnTransfer->Connect(IDB_TRANSFER, wxEVT_COMMAND_BUTTON_CLICKED,
                          wxCommandEventHandler(CAccountViewer::OnNewTransaction) );
}

and when one of the new transaction buttons are clicked :

Code:

void CAccountViewer::OnNewTransaction(wxCommandEvent &event)
{
    bool IsXfer = false;
    CTransactionViewer *pTransactionViewer;
    STransaction Transaction;
    Transaction.TransactionNumber = m_pAccount->GetNewTransactionNumber();
    Transaction.TransferNumber = 0;
    Transaction.AccountName = m_pAccount->GetAccountName();
    Transaction.Cleared = TS_OPEN;

In red is where the seg faults occur. I don't quite understand this since m_pAccount is a valid pointer in the constructor for CAccountViewer and then suddenly is not??!??