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POC++ List destructor called after every use of List's method
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  1. POC++ List destructor called after every use of List's method
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    copied!<p>This is a follow up to a question I asked earlier today regarding the appropriation of directly calling a class' destructor.</p> <p>I'm creating my own List for an assignment. I have overloaded the assignment, square brackets, in and out stream operators and have the basic adding, removing and printing to screen functionality.</p> <p>My next step is to have the List delete and release the memory of all of its nodes, which I am having trouble with.</p> <p>I have the List write to the screen its current state after performing its operations, as follows:</p> <pre><code>void main() { // Create instance of list List aList(true); List bList(true); aList.Add(1); aList.Add(2); bList.Add(2); cout &lt;&lt; "aList: " &lt;&lt; aList; cout &lt;&lt; "bList: " &lt;&lt; bList; aList = bList; cout &lt;&lt; "aList: " &lt;&lt; aList; cout &lt;&lt; "bList: " &lt;&lt; bList; aList.Add(3); cout &lt;&lt; "aList: " &lt;&lt; aList; cout &lt;&lt; "bList: " &lt;&lt; bList; int i = 0; cin &gt;&gt; i; } </code></pre> <p>Here is my overloaded out stream:</p> <pre><code>ostream &amp;operator&lt;&lt;(ostream &amp;stream, List theList) { stream &lt;&lt; "There are " &lt;&lt; theList._totalNodes &lt;&lt; " nodes in the list." &lt;&lt; endl; for(int i = 0; i &lt; theList._totalNodes; i++) { stream &lt;&lt; "Node #" &lt;&lt; i &lt;&lt; " holds the data: " &lt;&lt; theList[i] &lt;&lt; endl; } return stream; } </code></pre> <p>Looking at the command prompt window after this is used "Destructor called" is also printed underneath it.</p> <p>The List destructor:</p> <pre><code>List::~List() { cout &lt;&lt; "Destructor called" &lt;&lt; endl; // List::Destroy(); } </code></pre> <p>The overloaded assignment operator also seems to call the destructor, which doesn't surprise me. However, the others do.</p> <pre><code>List &amp;List::operator=(List &amp;aList) { // Make sure not the same object trying to be copied if(this != &amp;aList) { // Perform deep copy // Delete old pointers in redundant list, only if they exist already if(_head) { delete _head, _tail, _current, _del; _totalNodes = 0; // Reset total nodes } // Now set new pointers copied from other list _head = NULL; _tail = _head; _current = _head; _del = _head; // Now loop through all nodes in other list and copy them to this // Reset pointer in other list aList.Reset(); for(int i = 0; i &lt; aList._totalNodes; i++) { Add(aList.Current()-&gt;_data); aList.Next(); } // Reset other list's pointer aList.Reset(); Reset(); // Reset our pointer } return *this; // Return for multi assignment } </code></pre> <p>I also have the destructor to a List write "Destructor called" when it's called and noticed that it is called after every use of one of its methods.</p> <p>Why is this? I assumed the destructor is called when the object is no longer needed, i.e. deleted.</p> <p>Furthermore, when stepping through my code I have noticed that when a pointer is deleted the memory address it is pointing to isn't being nullified. Do I have to manually NULL a pointer after it is deleted?</p>
 

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