C++ method declaration is incompatible with - c++

Question

Here is a simple c++ class for binary tree. Compiler throws an error:
E0147 declaration is incompatible with "void BinaryTree::getLeftChild(node *n)"
Here node is a struct defined under the private section in the class. I am not sure why it says incompatible declaration.
//------------------------ BinaryTree class-----------------
class BinaryTree
{
public:
BinaryTree();
~BinaryTree();
void createRootNode();
void getChildren();
void getLeftChild(node* n);
void getRightChild(node* n);
private:
typedef struct node
{
node *lchild = nullptr;
int data;
node *rchild = nullptr;
}node;
queue <node*> Q;
node *root;
};
BinaryTree::BinaryTree()
{
createRootNode();
getChildren();
}
void BinaryTree::createRootNode()
{
root = new node();
cout << "Enter value for root node" << endl;
cin >> root->data;
Q.push(root);
}
void BinaryTree::getChildren()
{
while (Q.empty == false)
{
getLeftChild(Q.front());
getRightChild(Q.front());
Q.pop();
}
}
void BinaryTree::getLeftChild(node* n)
{
}
void BinaryTree::getRightChild(node* n)
{
}
Code picture with errors

Answer 1

I got another struct in global scope declared as "node" which created chaos. Secondly, i also need to fix the order of public and private sections.
Here is working code
//------------------------ BinaryTree class-----------------
class BinaryTree
{
private:
typedef struct node
{
node *lchild = nullptr;
int data;
node *rchild = nullptr;
}node;
queue <node*> Q;
node *root;
public:
BinaryTree();
~BinaryTree();
void createRootNode();
void getChildren();
void getLeftChild(node* n);
void getRightChild(node* n);
};
BinaryTree::BinaryTree()
{
createRootNode();
getChildren();
}
void BinaryTree::createRootNode()
{
root = new node();
cout << "Enter value for root node" << endl;
cin >> root->data;
Q.push(root);
}
void BinaryTree::getChildren()
{
while (Q.empty() == false)
{
getLeftChild(Q.front());
getRightChild(Q.front());
Q.pop();
}
}
void BinaryTree::getLeftChild(node* n)
{
}
void BinaryTree::getRightChild(node* n)
{
}

Answer 2

First error, is that you need to forward declare the node.
Second error, is that you are trying to access node which is privately declared inside of BinaryTree.
First answer:
typedef struct node
{
node* lchild = nullptr;
int data;
node* rchild = nullptr;
}node;
class BinaryTree
{
public:
BinaryTree();
~BinaryTree();
void createRootNode();
void getChildren();
void getLeftChild(node* n);
void getRightChild(node* n);
private:
node* root;
};
void BinaryTree::getLeftChild(node* n)
{
}
void BinaryTree::getRightChild(node* n)
{
}
Now code compiles fine.
Or if you want to have the typedef defined as private inside, you need the implementation to be inside the class as well.
Second Answer:
typedef struct node;
class BinaryTree
{
public:
BinaryTree();
~BinaryTree();
void createRootNode();
void getChildren();
void getLeftChild(node* n)
{
}
void getRightChild(node* n)
{
}
private:
typedef struct node
{
node* lchild = nullptr;
int data;
node* rchild = nullptr;
}node;
node* root;
};