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Lesson 16 Coding COM methods 2
Objective Add code to implement IManagePhBook.

Coding COM Methods IManagePhBook

Our last set of tasks is to add code for IManagePhBook, AddPhoneRec, and DeletePhoneRec.
Adding a phone record is easy. If m_PhRecs has room, we add it to the end.
STDMETHODIMP CPhBookObj::AddPhoneRec
  (PhRec *pPhRec, BOOL *pOK)
  
{
  //See if we still have room for another record.
  if (m_numrecs < MAX_RECS - 1)
  {
  m_PhRecs[m_numrecs] = *pPhRec;

  //if m_currec is not set, set it
  if (m_currec == -1)
    m_currec = m_numrecs;

    ++m_numrecs;
    *pOK = TRUE;
  }
  else
  {
    *pOK = FALSE;
  }
  return S_OK;
}
DeletePhoneRec deletes the current phone record, CurRec. Because we always add new records to the end of the collection of phone records, after deleting a record we have to compact the m_PhRecs array. We move all records above the deleted record down one position in m_PhRecs. DeletePhoneRecord must also handle a special case; When the last record in the list is deleted, m_currec must be moved to a valid index.


STDMETHODIMP CPhBookObj::DeletePhoneRec (BOOL *pOK){
//If we don't have any records - we can't
//delete any!
   
  if (m_numrecs == 0 || m_currec == -1)
  {
    *pOK = FALSE;
  }
    else
  {
//Move all of the records above the deleted
//slot down. If we are deleting the last record
//the loop won't execute.
    
    int idx;
    for (idx = m_currec; idx <
    m_numrecs - 1; ++idx)
    
    {
    m_PhRecs[idx] = m_PhRecs[idx + 1];
    }
//Clear the spot vacated by the record with the
//highest index. Call Win32 API function
//ZeroMemory.

    ZeroMemory(&m_PhRecs[idx],
      sizeof(PhRec));
 
//If we deleted the last record, we need to
//change m_currec to a valid index. We also
//have a special case here when there is only
//one record and we delete it. For this case
//m_currec has to be reset to -1 to tell callers
//it is not set. This check handles both cases.

    if (m_currec == m_numrecs - 1)
    {
      --m_currec;
    }
    --m_numrecs;
    *pOK = TRUE;
  }
  return S_OK;
}

Add Methods to IManagePhBook - Exercise

Click the Exercise link below to apply what you have learned about adding methods to IManagePhBook.
Add Methods to IManagePhBook - Exercise