How to print Binary tree search recursively inorder

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C++

Hello there,

I tried to make an implementation of a function in my header that prints recursively by inorder method a binary tree search (printing each node from the lowest value to the biggest)

The function itself do not take any parameters
I tried to do this on my own for more than a few hours now.

I will be happy if anyone could help me figure this out

These are the implementations:

void BSNode::printNodes() const //prints the smallest _data value to the biggest
{
	if (_left == NULL)
	{
		cout << _data << endl;
	}
	else
	{
		return _left->printNodes();
	}

	if (_right == NULL)
	{
		cout << _data << endl;
	}
	else
	{
		return _right->printNodes();
	}
}

BSNode::BSNode(string data)
{
	_data.clear();
	_data.assign(data);
        _count=1;
	
	_right = NULL;
	_left = NULL;
}

BSNode::BSNode(const BSNode& other)
{
	_data.clear();
	_data.assign(other._data);
	_count = other._count;

	_right = other._right;
	_left = other._left;
}

BSNode::~BSNode()
{
	delete _right;
	delete _left;
	_data.clear();
        _count =0;
}

The header is:

class BSNode
{
public:
	BSNode(string data);
	BSNode(const BSNode& other);
	~BSNode();
	void insert(string value);
	string getData() const;
	BSNode* getLeft()const ;
	BSNode* getRight() const;	
	void printNodes() const;//prints the smallest _data value to the biggest

private:

	BSNode* _left;
	BSNode* _right;
	string _data;
	int _count;