Class help

[lapidusva25]

Hi guys,

So I'm very new to C++. rusty with dev, and need some help.

I am using the treeView class, which contains contains an extension: treeNode class. I would like to add a variable to the treeNode class to include a string variable named strData. So that when a Node in a tree is selected I can say treeView1->SelectedNode::strData and it'll pull the string.

This is what I think it would look like:

#include <string>

class treeNode{
public:
string strData;
};

I realize that I should probably make strData private, and have a get/set function, but i'd like to keep it simple for now.

Follow up question: (once this is working, would this be the correct way to get the string? treeView1->SelectedNode::strData)

Many thanks!

[yulingo]

Well I think you've already read the C++ tutorial on classes, and your class looks fine.

You're using the wrong operator. :: is the scope resolution operator, and doesn't apply to members of a class. You should be using the . operator to access members. (-> is a shortcut operator used when dereferencing pointers). Maybe you should brush up on the differences between references, pointers, values, etc.

[lapidusva25]

So the fact that the treeNode class already exists doesn't matter? I can just define more items in it without letting C++ know that it already exists?

[lapidusva25]

So I think I explained my question wrong, I want to add something to an existing class:

System::Windows::Forms::TreeNode

When I compiled the code with the above mentioned class definition and tried to set the string variable with:

treeView1->SelectedNode->strData = "abba";

I got this error:

Error 2 error C2039: 'strData' : is not a member of 'System::Windows::Forms::TreeNode' c:\users\lapidusva25\documents\visual studio 2010\projects\jobapply\jobapply\Form1.h 253 1 JobApply

[norm b]

Try inheriting from TreeNode:

class treeNode : public TreeNode {
public:
string strData;
};

And then add treeNode(s) to treeView1.

[lapidusva25]

Tried and got this error:


Error 1 error C3625: 'MegaNode': an unmanaged type cannot derive from a managed type 'System::Windows::Forms::TreeNode' C:\Users\lapidusva25\documents\visual studio 2010\Projects\JobApply\JobApply\JobApply.cpp 7 1 JobApply

[lapidusva25]

And this when I named it TreeNode:

Error 2 error C2499: 'TreeNode' : a class cannot be its own base class C:\Users\lapidusva25\documents\visual studio 2010\Projects\JobApply\JobApply\JobApply.cpp 7 1 JobApply


This when I tried treeNode:

Error 1 error C3625: 'treeNode': an unmanaged type cannot derive from a managed type 'System::Windows::Forms::TreeNode' C:\Users\lapidusva25\documents\visual studio 2010\Projects\JobApply\JobApply\JobApply.cpp 7 1 JobApply

[yulingo]

You're using C++/CLI, which means that your derived class has to be a ref class.

it's possible to have composite classes in C++/CLI with both managed and unmanaged objects, but derived objects must always be the same type.

Why are you using C++/CLI for your forms project and not C#?