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POuser defined variables on the heap getting destroyed in while loop
 

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  1. POuser defined variables on the heap getting destroyed in while loop
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    <p>I an odd problem that i cant understand if someone could point me in the right direction it would be greatly appreciated.I create my own linked list variables on the heap but when i go to add another variable to it they all get destroyed and i dont know why. in my main i set up my variables like this<br> <strong>main.cpp</strong> </p> <pre><code> Book* temp; temp = bookSetUp(); </code></pre> <p>this goes to a different cpp called functions which sets up the objects like this:<br> <strong>functions.cpp</strong> </p> <pre><code> Book* bookSetUp() { //The items that populate the list Book* a= new Book("A Tale of Two Cities", "Charles Dickens", "1", true); Book* b= new Book("Lord of the rings", "J.R.R Tolkein", "2", true); Book* c= new Book("Le Petit Prince", "Antoine de Saint-Exupéry", "3", true); Book* d= new Book("And Then There Were None", "Agatha Christie", "4", true); Book* e= new Book("Dream of the Red Chamber","Cao Xueqin","5", true); Book* f= new Book("The Hobbit","J.R.R Tolkein","6", true); //sets up the pointers between books a-&gt;setPrev(NULL); a-&gt;setNext(b); b-&gt;setPrev(a); b-&gt;setNext(c); c-&gt;setPrev(b); c-&gt;setNext(d); d-&gt;setPrev(c); d-&gt;setNext(e); e-&gt;setPrev(d); e-&gt;setNext(f); f-&gt;setPrev(e); f-&gt;setNext(NULL); //sets up a temp pointer to a Book* temp = a; //returns the temp pointer to a return temp; } </code></pre> <p>this works perfectly but later on when i go to add to the list again in the main using:<br> <strong>main.cpp</strong> </p> <pre><code>else if(checkRegUser(username, password, regUserList) == true) { int choice = 99; cout &lt;&lt; "Welcome Registered user: "&lt;&lt; username &lt;&lt; endl; while(choice != 0) { //this is so the print will start everytime as if you run it once print will be at NULL thereafter Book* print = temp; choice = options(); if(choice == 1) { while(print!=NULL) { cout&lt;&lt;"Name: "&lt;&lt;print-&gt;getName()&lt;&lt;endl&lt;&lt;"Author: "&lt;&lt;print-&gt;getAuthor()&lt;&lt;endl&lt;&lt;"ISBN: "&lt;&lt;print-&gt;getISBN()&lt;&lt;endl&lt;&lt;"Availability: "&lt;&lt;print-&gt;getAvail()&lt;&lt;endl; cout&lt;&lt;endl; print = print-&gt;getNext(); } print = temp; } if(choice == 2) { search(temp); } if(choice == 3) { takeOut(temp); } if(choice == 4) { returnBack(temp); } if(choice == 5) { append(temp); } if(choice == 6) { cout&lt;&lt;"Sorry you have the privilege needed to use this function."&lt;&lt;endl; } if(choice == 7) { choice = 0; } } } </code></pre> <p>My user defined variables get destroyed. I debugged and they just disappeared i am not sure why!<br> Just in-case its needed here is my add() function because I feel It could be me missing something small or just making a disastrous mistake. My add function is in the functions.cpp and I know all the links are working as I have everything else running apart from this<br> <strong>functions.cpp</strong> </p> <pre><code>Book* append(Book* tempParam) { string title; string author; string isbn; bool avail; cout&lt;&lt;"What is the book called?"&lt;&lt;endl; cin.clear(); cin.ignore(); getline(cin, title); cout&lt;&lt;"Who is the author?"&lt;&lt;endl; cin.clear(); cin.ignore(); getline(cin, author); cout&lt;&lt;"What is the ISBN to be?"&lt;&lt;endl; cin&gt;&gt;isbn; Book* temp = new Book(title, author, isbn, true); Book* list = tempParam;int count; while(list!=NULL) { if(list-&gt;getNext()==NULL&amp;&amp;list-&gt;getName()!=title) { list-&gt;setNext(temp); temp-&gt;setNext(NULL); temp-&gt;setPrev(list); cout&lt;&lt;"Your book has been added"&lt;&lt;endl; cout&lt;&lt;temp-&gt;getName()&lt;&lt;temp-&gt;getAuthor()&lt;&lt;endl; } list = list-&gt;getNext(); } tempParam = list; return tempParam; } </code></pre> <p>My user defined classes are working perfectly its just when I go to add that my list gets destroyed any ideas??</p>
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    1. PO
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      1. PTAnswer
    1. This table or related slice is empty.
    1. PTQuestion
    1. USDennington-bear
    1. USDennington-bear
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    1. This table or related slice is empty.
    1. This table or related slice is empty.
    1. This table or related slice is empty.
    1. PO
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      1. PTAnswer
    1. This table or related slice is empty.
    1. COIs it `add` or `append`? Could you prepare a [minimal complete example](http://sscce.org)?
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      1. POuser defined variables on the heap getting destroyed in while loop
      1. USBeta
    2. COI think we need more of main.
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      1. POuser defined variables on the heap getting destroyed in while loop
      1. USRichardPlunkett
    3. CObtw, it's not your error, but Book* append(Book* tempParam) doesn't work when you pass it an empty list.You should fix that.
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      1. POuser defined variables on the heap getting destroyed in while loop
      1. USRichardPlunkett
 

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