'.' 之前应有主要表达式代币

我已经为此奋斗了一段时间并环顾四周，但我不确定我做错了什么

错误：

错误：“.”标记之前应有主表达式

addElement 方法内的大部分代码都会弹出 涉及 BinaryNode.variable 但我完全不知道在这里要做什么

#include <cstdlib>
#include "BinarySearchTree.h"
using namespace std;

template <typename Comparable>
BinarySearchTree<Comparable>::BinarySearchTree(const Comparable & theElement, BinarySearchTree<Comparable> *leftTree,
BinarySearchTree<Comparable> *rightTree) : BinaryNode(theElement,leftTree,rightTree) {
}

template <typename Comparable> 
void BinarySearchTree<Comparable>::addElement(Comparable newElement) {
    if(newElement < BinaryNode.element) {
        if(BinaryNode.left == NULL) {
            BinaryNode.left = BinarySearchTree(newElement, NULL, NULL);
            BinaryNode.right.root = BinaryNode;
        } else {
            BinaryNode.left.addElement(newElement);
        }
    } else if (newElement > BinaryNode.element) {
        if(BinaryNode.right == NULL) {
            BinaryNode.right = BinarySearchTree(newElement, NULL, NULL);
            BinaryNode.right.root = this;
        } else {
            BinaryNode.right.addElement(newElement);
        }
    }

这是 BinarySearchTree 的头文件

#include <vector>
using namespace std;

template<typename Comparable>
class BinarySearchTree {
public:
    BinarySearchTree(const Comparable & theElement, BinarySearchTree<Comparable> * leftTree, 
        BinarySearchTree<Comparable> * rightTree);
    void addElement(Comparable newElement);
    void removeElement(Comparable newElement);
    BinarySearchTree<Comparable> * findElement(Comparable newElement);
    bool isEmpty();
    BinarySearchTree & operator=(const BinarySearchTree &tree);
    vector<BinarySearchTree> preOrder(vector<BinarySearchTree> * list);
    vector<BinarySearchTree> inOrder();
    vector<BinarySearchTree> postOrder();

private:
    struct BinaryNode {
        Comparable element;
        BinarySearchTree<Comparable> *left;
        BinarySearchTree<Comparable> *right;

        BinaryNode( const Comparable & theElement, BinarySearchTree<Comparable> *leftTree,
        BinarySearchTree<Comparable> *rightTree) : element(theElement), left(leftTree), right(rightTree){}
     };

     BinaryNode *root;
 };

你正在尝试使用BinaryNode作为变量名，但它是一种类型。你不能使用.类型上的运算符，仅对象上的运算符。例如：

if(newElement < root->element) {
    if(root->left == NULL) {
        root->left = BinarySearchTree(newElement, NULL, NULL);
        root->right->root = new BinaryNode;
    } else {
        root->left->addElement(newElement);
    }

注意我改为->同样，因为到处都有指针。