IAutoComplete tutorial

[kingting]

Hi All,

I have been using this tutorial to implement Auto completion in one of my text boxes. However I don't understand what they mean by Implementing IEnumString...

I've looked at this link http://www.codeproject.com/Articles/...-implementatio and they skip the actual reasoning and explanation of the implementation. I guess it is just my unfamiliarity with Interfaces in general. You take a new object (say CCustomAutoComplete) and implement the following functions as (public/private?) functions:

Clone(), Next(), Reset(), Skip()

the question is... how do you know how they are implemented? is each CCustomAutoComplete just a string that links to another CCustomAutoComplete (like a linked list?) Can I use TCHARS?

Thanks for the help.. I'm quite clueless on COM and OOP

MSDN Tutorial:

http://msdn.microsoft.com/en-us/libr...(v=vs.85).aspx

UPDATE:

I've created a skeleton for the new class:

My questions are:

1) am I on the right track here? Am I even defining this class correctly, and do i need more auxiliary functions and members and what not?
2) Is it OK to create the object using a pointer to an array of TCHAR arrays (essentially a TCHAR **)?
3) How does memory allocation work in this case?
4) Do I even need the COM IUnknown implementation if this is just a simple enumString implementation (I don't think IenumString is derived from IUnknown).

I probably have more questions but I can't think of anymore right now. I would also like to stick with a simple TCHAR implementation of this...

// custom auto complete 


class CCustomAutoComplete : public IEnumString
{

private:

	// Private members
        TCHAR  m_CurrList[256][64];
	ULONG m_nCurrentElement;
	ULONG m_nRefCount;
	BOOL m_fBound;


public:


	// Constructors/destructors

	CCustomAutoComplete()
	{
		InternalInit();

	}

	CCustomAutoComplete(TCHAR ** p_ArrayList)
	{
		InternalInit();

		SetList(p_ArrayList);

	}
	
	
	~CCustomAutoComplete()
	{
			// free array...?
	}

public:

	// Implementation

	BOOL SetList(TCHAR ** p_ArrayList)
	{

		return TRUE;

	}


	BOOL AddItem(TCHAR * p_Item)
	{

		return TRUE;

	}


	
	BOOL RemoveItem(TCHAR * p_RemoveItem)
	{

		return TRUE;
	}


	BOOL Clear()
	{


		return TRUE;

	}


public:

	//
	//	IUnknown implementation
	//
	STDMETHODIMP_(ULONG) AddRef()
	{
		return ::InterlockedIncrement(reinterpret_cast<LONG*>(&m_nRefCount));
	}

	STDMETHODIMP_(ULONG) Release()
	{
		ULONG nCount = 0;
		nCount = (ULONG) ::InterlockedDecrement(reinterpret_cast<LONG*>(&m_nRefCount));

		if (nCount == 0)
			delete this;

		return nCount;

	}

	STDMETHODIMP QueryInterface(REFIID riid, void** ppvObject)
	{

		HRESULT hr = E_NOINTERFACE;
		
		if (ppvObject != NULL)
		{
			*ppvObject = NULL;

			if (IID_IUnknown == riid)
				*ppvObject = static_cast<IUnknown*>(this);

			if (IID_IEnumString == riid)
				*ppvObject = static_cast<IEnumString*>(this);

			if (*ppvObject != NULL)
			{
				hr = S_OK;
				((LPUNKNOWN)*ppvObject)->AddRef();
			}

		}
		else
		{
			hr = E_POINTER;
		}
		
		return hr;

	}

public:

	//
	//	IEnumString implementation
	//
	STDMETHODIMP Next(ULONG celt, LPOLESTR* rgelt, ULONG* pceltFetched)
	{

	

		return S_OK;
	}
 
	STDMETHODIMP Skip(ULONG celt)
	{
		

		return S_OK;
	}
 
	STDMETHODIMP Reset(void)
	{
		
		return S_OK;
	}
 
	STDMETHODIMP Clone(IEnumString** ppenum)
	{

		return S_OK;

	}

private:

	// Internal implementation

	void InternalInit()
	{

		m_nCurrentElement = 0;
		m_nRefCount = 0;
		m_fBound = FALSE;


	}

	

};