Why can't I create a pointer to a TTreeNode in a TTreeView - c++builder-10.4-sydney

Question

Using C++ Builder in Rad Studio 10.4
Why can't I create a pointer to a TTreeNode?
I have a TTreeView called BookmarksTree, and I want to loop through all of its nodes. When I try and compile this:
TTreeNode *Node;
Node = BookmarksTree->Items[1];
I get a compiler error:
assigning to 'Vcl::Comctrls::TTreeNode *' from incompatible type 'Vcl::Comctrls::TTreeNodes'
According to Vcl.ComCtrls.TCustomTreeView.Items, I should be able to use
MyTreeNode = TreeView1->Items[[1]];
Has anyone any idea what's wrong here?

Answer 1

BookmarksTree->Items is a pointer to a single TTreeNodes object. You are trying to perform pointer arithmetic to access a node as if the Items were an array of TTreeNode* pointers, which is simply not the case.
You need to use the TTreeNodes::Item[] sub-property instead, eg:
int count = BookmarksTree->Items->Count;
for(int i = 0; i < count; ++i)
{
TTreeNode *Node = BookmarksTree->Items->Item[i];
...
}
Alternatively, you can use the TTreeNodes::operator[], but that requires you to dereference the TTreeNodes* pointer first, eg:
int count = BookmarksTree->Items->Count;
for(int i = 0; i < count; ++i)
{
TTreeNode *Node = (*(BookmarksTree->Items))[i];
...
}
Alternatively, in the Clang-based compilers only, you can use C++ iterators, per C++ Iterator Support for Delphi Enumerable Types and Containers, eg:
auto iter = std::begin(BookmarksTree->Items);
auto end = std::end(BookmarksTree->Items);
while (iter != end)
{
TTreeNode *Node = *iter++;
...
}
Or a range-for loop (which uses iterators internally):
for(TTreeNode *Node : BookmarksTree->Items)
{
...
}