The simplest collections to use are CStringList, CStringArray, CList, CArray

Collections

The simplest collections to use are CStringList and CStringArray. A list of other things, such as a list or array of integers, can easily be created using template classes such as CList and CArray.

CStringList

The following is a simple sample of using a CStringList. The first thing to do is to define a variable, as in:

CStringList StringList;

Then add entries, as in:

StringList.AddTail("A string");

Then iterating through the list could be as easy as in the following:

	CString String;
POSITION Position = StringList.GetHeadPosition();
while (Position)
	String = StringList.GetNext(Position);

Notice that there is not any clean-up necessary beyond the default destructor. When the CStringList is deleted, all strings are also deleted. This is different when a collection contains pointers, because then the data pointed to must be deleted prior to deleteing the collection.

CList

The following is a simple sample of using a CList. This sample is kept especially simple by making it a list of integers. The first thing to do is to make a typedef, as in:

typedef CList  CListType;

Next, use the typedef as in the following:

CListType List;

Then add entries as in (where "i" is an "int"):

List.AddTail(i);

Finally, iterate through the list as in the following:

	int i;
POSITION Position = List.GetHeadPosition();
while (Position)
	i = List.GetNext(Position);

Notice that since the list contents are not pointers, as in the case of a CStringList, there is not any clean-up necessary.

CObList

If it is necessary to store a class or struct, a CObList can be used. The following is a simple sample of using a CObList:

class CStringObject : public CObject {
	DECLARE_DYNAMIC(CStringObject)
public:
        CString m_String;
};

IMPLEMENT_DYNAMIC(CStringObject, CObject)

    CStringObject *pStringObject;
    POSITION ObjectListPos;
    CObList ObjectList;
pStringObject = new CStringObject;
pStringObject->m_String = "First Object";
ObjectListPos = ObjectList.AddTail(pStringObject);
pStringObject = new CStringObject;
pStringObject->m_String = "Last Object";
ObjectListPos = ObjectList.AddTail(pStringObject);

ObjectListPos = ObjectList.GetHeadPosition();
while (ObjectListPos!=NULL) {
    pStringObject = (CStringObject *) ObjectList.GetNext(ObjectListPos);
    TRACE1("%s\n", pStringObject->m_String);
    delete pStringObject;
    }
ObjectList.RemoveAll();

CTypedPtrMap

The following is an example of using CTypedPtrMap.

class CRecord {
public:
    int m_Index;
};

typedef CTypedPtrMap <CMapStringToPtr, CString, CRecord *> CRecords;

    CRecords m_Records;

    CString String;
    CRecord *pRecord;
m_Records.SetAt(String, pRecord);

Position = m_Records.GetStartPosition();
while (Position!=NULL) {
    m_Records.GetNextAssoc(Position, String, pRecord);
    TRACE("%s %i\n", String, pRecord->m_Index);
    delete pRecord;
    }
m_Records.RemoveAll();

CMap

The following is an example of using CMap.

typedef CMap  CIntegerMap;

    CIntegerMap m_IntegerMap;

    CString String;
    int Index;
m_IntegerMap.SetAt(Index, CString(String));

Position = m_IntegerMap.GetStartPosition();
while (Position!=NULL) {
	m_IntegerMap.GetNextAssoc(Position, Index, String);
	m_Outputfile.WriteString(String);
	String.Format(" %i\n", Index);
	m_Outputfile.WriteString(String);
	}
m_IntegerMap.RemoveAll();

Note: the default hash key for CMap is a DWORD, so unless you override CMap's HashKey function, the hash key cannot be more than four bytes. Microsoft Knowledge Base article Q158541 ("PRB: C2440 Error When Using CMap and User Defined Key Type") provides a sample of CMap with a HashKey override to allow use of a user-defined class for a key.

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