TreeView Design

[earthwormgaz]

I am trying to come up with a design for a tree/list view.

The list wants to be able to take any data type, and an object it can
use to render it in the tree. The trouble starts when you have a
variable number of columns.

Below is my current thinking, as inspired by the GTKmm and Qt
interfaces. The problem is the creeping effect of the templates. By
having a base class "TreeModelColumnBase" that isn't templated, and
then a templated derivation, I can have as many columns as I like in
"TreeModelColumnRecord". But how can I set values in it without the
templates creeping there way up to the "TreeModel"?

Hopefully this makes sense, any help is greatly appreciated.

<code>
class TreeModelColumnBase
{
template <typename T>
bool operator = (const T & _Val)
{
// TODO: what can i do here?
}
};

template <typename T, typename Renderer>
class TreeModelColumn : public TreeModelColumnBase
{
private:
Renderer m_Renderer;
T m_ColumnData;
};

class TreeModelColumnRecord
{
private:
std::list<TreeModelColumnBasem_ColumnsList;
};

class TreeModel
{
Iterator begin()
{
return m_RowsList.begin();
}
private:
std::list<TreeModelColumnRecordm_RowsList;

};

[earthwormgaz]

To make this clearer.

The problem really is how can I have a container that stores various
instances of a templated class, and be able to meaningfully interact
with the classes in that container. For example, assign them.

struct Base;

template <typename T>
struct Derived { T member; };

std::list<Base *myList;

for(std::list<Base *>::iterator it = myList.begin(); it !=
myList.end(); ++ it)
{
it->member = ???
}