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POHow to retrieve data out of a private string
 

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  1. POHow to retrieve data out of a private string
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    <p>For a school project I am trying to make a binary search tree at the same time we are supposed to learn how to use 'friendship' in classes. The errors I get while compiling are: [I put comments in code where the errors originate from for clarity] (Keep in mind I am not allowed to nest Node in the BST class they are both supposed to be in separate files and classes for the sake of this programming assignment)</p> <pre><code>BST.cpp: In member function `void BST::insert(std::string, std::string)': BST.cpp:11: error: `get_key' undeclared (first use this function) BST.cpp:11: error: (Each undeclared identifier is reported only once for each function it appears in.) BST.cpp: At global scope: BST.cpp:5: warning: unused parameter 'data' makefile.txt:9: recipe for target `BST.o' failed make: *** [BST.o] Error 1 </code></pre> <p>I want to be able to access the functions in Node.cpp to be able to retrieve its private members for the sake of the binary search tree. In BST.cpp so far I am attempting to compare a string 'key' that is passed into the 'insert' function with the string that 'xPtr' is currently pointing to. The classes are defined as: Node.h (directly below)</p> <pre><code>#ifndef NODE_H_INCLUDED #define NODE_H_INCLUDED #include &lt;iostream&gt; #include &lt;string&gt; using namespace std; class BST; class Node { public: Node(string key, string data) {m_key = key; m_data = data;} ~Node(); string get_key(Node *ptr); //takes in ptr to node and returns its key string get_data(Node *ptr); //takes in ptr to node and returns its data Node* get_left(Node *ptr); //takes in ptr to node and returns its left child pointer Node* get_right(Node *ptr); //takes in ptr to node and returns its right child pointer private: string m_key; string m_data; Node *m_left; Node *m_right; }; #endif // NODE_H_INCLUDED </code></pre> <p>Node.cpp</p> <pre><code>#include "Node.h" string Node::get_key(Node* ptr) { return ptr-&gt;m_key; } string Node::get_data(Node* ptr) { return ptr-&gt;m_data; } Node* Node::get_left(Node* ptr) { return ptr-&gt;m_left; } Node* Node::get_right(Node* ptr) { return ptr-&gt;m_right; } </code></pre> <p>BST.h</p> <pre><code>#ifndef BST_H_INCLUDED #define BST_H_INCLUDED #include &lt;iostream&gt; #include &lt;string&gt; using namespace std; class BST { public: BST() {m_root = NULL;} ~BST(); void insert(string key, string data); void find(string key); void remove(string key, string data); void print(); friend class Node; private: Node* m_root; }; #endif // BST_H_INCLUDED </code></pre> <p>BST.cpp</p> <pre><code>#include "BST.h" #include "Node.h" void BST::insert(string key, string data) { Node* yPtr = NULL; Node* xPtr = m_root; while(xPtr != NULL) { yPtr = xPtr; if(key &lt; get_key(xPtr)) //error: 'get_key' undeclared (first use this function) { } } } </code></pre>
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