CList Iterator

Introduction

MFC's CList provides a template linked list implementation and works perfectly adequately. However, iterating through the list can be a little combersome. Code like that below is common place for processing list elements, but the POSITION variable is meaningless and confusing as it always points to the next node rather than the current one.

POSITION        pos;
CList<int, int> list;

// add nodes to the list

pos = list.GetHeadPosition();
while (pos)
{
    int nElement;

    nElement = list.GetNext(pos);
    // do something with nElement
}

TLListIter class

The iterator class I present here simplifies the use slightly, making the code easier to read and maintain. It originates from a larger project I wrote where I have a list of objects of type A, each with their own list of objects of type B, and I needed to iterate all objects of type B in the system. This class simplified the task immensly.

So using this class, the above code becomes

CList<int, int>      list;		// linked list
TLListIter<int, int> iter(list);	// linked list iterator
// add nodes to the list

iter.begin();
while (iter)
{
    int nElement;

    nElement = iter++;
    // do something with nElement
}

Public Members

Construction/Destruction

TLListIter(TLListIter<TYPE, ARG_TYPE> &__iter);
Copy constructor to create a new iterator for the same linked list with the same node position.

virtual ~TLListIter();
Virtual class destructor.

Operators

operator ARG_TYPE ();
Linked List argument operator will returns the element at the current node.

Navigation

TLListIter<TYPE, ARG_TYPE> operator--(int);
Post decrement operator returns the current node and moves the internal position to the previous node.

// these functions will return false if there are no elements in the list

bool begin(void);
Moves to the first node in the list. This function returns false if the linked list is empty.

bool end(void);
Moves to the last node in the list. This function returns false if the linked list is empty.

MFC Compatibilty

Returns the internal POSITION variable.

Limitations

• As the class stands, it cannot be used to process a list of bool. This is because of the operator bool() used to determine the end of the list.
• For some reason unknown to me (please let me know any solutions) a compiler error is generated if the class is used while (nNumber == 7 && iter). Instead, this must be coded while (nNumber == 7 && iter == true) and then all is fine. Wierd.

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