C++繼承/未聲明的標識符問題

Question

我從我的一本教科書的同伴網站下載了一些C++文件。我將這些文件添加到Xcode中，然後我編寫了一個函數來測試我下載的類。

這兩個文件是二叉樹的類，然後是從二叉樹類繼承的二叉搜索樹的類。

我的問題是，超類的成員之一是沒有得到聲明時，子類繼承超類。我遵循我見過的所有例子，但沒有看到問題。我發佈了下面的相關代碼以及我得到的錯誤。

binaryTree.h：

#include <iostream> 

using namespace std; 

    //Definition of the node 
template <class elemType> 
struct binaryTreeNode 
{ 
    elemType info; 
    binaryTreeNode<elemType> *llink; 
    binaryTreeNode<elemType> *rlink; 
}; 

    //Definition of the class 
template <class elemType> 
class binaryTreeType 
{ 
public: 
    const binaryTreeType<elemType>& operator= 
       (const binaryTreeType<elemType>&); 
     //Overload the assignment operator. 
    bool isEmpty() const; 
     //Returns true if the binary tree is empty; 
     //otherwise, returns false. 
    void inorderTraversal() const; 
     //Function to do an inorder traversal of the binary tree. 
    void preorderTraversal() const; 
     //Function to do a preorder traversal of the binary tree. 
    void postorderTraversal() const; 
     //Function to do a postorder traversal of the binary tree. 

    int treeHeight() const; 
     //Returns the height of the binary tree. 
    int treeNodeCount() const; 
     //Returns the number of nodes in the binary tree. 
    int treeLeavesCount() const; 
     //Returns the number of leaves in the binary tree. 
    void destroyTree(); 
     //Deallocates the memory space occupied by the binary tree. 
     //Postcondition: root = NULL; 

    binaryTreeType(const binaryTreeType<elemType>& otherTree); 
     //copy constructor 

    binaryTreeType(); 
     //default constructor 

    ~binaryTreeType(); 
     //destructor 

protected: 
    binaryTreeNode<elemType> *root; 

private: 
    void copyTree(binaryTreeNode<elemType>* &copiedTreeRoot, 
        binaryTreeNode<elemType>* otherTreeRoot); 
     //Makes a copy of the binary tree to which 
     //otherTreeRoot points. The pointer copiedTreeRoot 
     //points to the root of the copied binary tree. 

    void destroy(binaryTreeNode<elemType>* &p); 
     //Function to destroy the binary tree to which p points. 
     //Postcondition: p = NULL 

    void inorder(binaryTreeNode<elemType> *p) const; 
     //Function to do an inorder traversal of the binary 
     //tree to which p points. 
    void preorder(binaryTreeNode<elemType> *p) const; 
     //Function to do a preorder traversal of the binary 
     //tree to which p points. 
    void postorder(binaryTreeNode<elemType> *p) const; 
     //Function to do a postorder traversal of the binary 
     //tree to which p points. 

    int height(binaryTreeNode<elemType> *p) const; 
     //Function to return the height of the binary tree 
     //to which p points. 
    int max(int x, int y) const; 
     //Returns the larger of x and y. 
    int nodeCount(binaryTreeNode<elemType> *p) const; 
     //Function to return the number of nodes in the binary 
     //tree to which p points 
    int leavesCount(binaryTreeNode<elemType> *p) const; 
     //Function to return the number of leaves in the binary 
     //tree to which p points 
}; 

binarySearchTree.h：

#include "binaryTree.h" 
#include <iostream> 
#include <cassert> 

using namespace std; 

template <class elemType> 
class bSearchTreeType: public binaryTreeType<elemType> 
{ 
public: 
    bool search(const elemType& searchItem) const; 
     //Function to determine if searchItem is in the binary 
     //search tree. 
     //Postcondition: Returns true if searchItem is found in the 
     // binary search tree; otherwise, returns false. 

    void insert(const elemType& insertItem); 
     //Function to insert insertItem in the binary search tree. 
     //Postcondition: If no node in the binary search tree has the 
     // same info as insertItem, a node with the info insertItem 
     // is created and inserted in the binary search tree. 

    void deleteNode(const elemType& deleteItem); 
     //Function to delete deleteItem from the binary search tree 
     //Postcondition: If a node with the same info as deleteItem 
     // is found, it is deleted from the binary search tree. 

private: 
    void deleteFromTree(binaryTreeNode<elemType>* &p); 
     //Function to delete the node to which p points is deleted 
     //from the binary search tree. 
     //Postcondition: The node to which p points is deleted from 
     // the binary search tree. 

而下面是我使用測試類的代碼：

#include <iostream> 
#include "binarySearchTree.h" 
using namespace std; 
void testBinarySearchTree(); 
int main() 
{ 
    testBinarySearchTree(); 

    return 0; 
} 
void testBinarySearchTree() 
{ 
    bSearchTreeType<int> myTree; 

    myTree.insert(50); 
    myTree.insert(40); 
    myTree.insert(30); 
    myTree.insert(60); 
    myTree.insert(70); 
    myTree.insert(45); 
    myTree.insert(65); 
    myTree.insert(55); 
} 

T我得到的錯誤是binaryTree超類的成員變量root沒有在創建對象bSearchTreeType時被聲明。

Answer 1

root是一個從屬名稱，這需要特殊考慮才能將其納入範圍或強制查找。你沒有包含訪問變量的代碼，但是這個代碼非常糟糕，我懷疑作者是否正確。

請讓我們知道這是BTW的書，所以它可以放在書籍清單，以避免。命名約定本身讓我想嘔吐。雖然還有一些明顯的技術缺陷，例如缺乏保護類型或虛擬析構類型的公共繼承...無緣無故。

要在bSearchTreeType<elemType>範圍內正確訪問root，您需要使用binaryTreeType<elemType>::root。

編輯：其實我認爲更正確地說，root你想要的是一個依賴名稱，除非你強迫它使用依賴名稱查找它不會。這意味着它在模板實例化之前查找依賴範圍之外的root，因此未找到您期望的root。作者可能使用了一個不使用兩階段查找的編譯器，如MSVC++ ......如果他們根本就不想編譯他們的示例代碼。編譯器應該執行兩階段查找。如果在範圍的某個地方存在非依賴的root名稱，則正確的編譯器將使用它而不是基類的版本。