62 lines
2.6 KiB
C++
62 lines
2.6 KiB
C++
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// fig20_13.cpp
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// Demonstrate use of weak_ptr.
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#include <fmt/format.h>
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#include <iostream>
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#include <memory>
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#include "Author.h"
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#include "Book.h"
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int main() {
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// create a Book and an Author
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std::shared_ptr<Book> bookPtr(
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std::make_shared<Book>("C++ How to Program"));
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std::shared_ptr<Author> authorPtr(
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std::make_shared<Author>("Deitel & Deitel"));
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// reference the Book and Author to each other
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bookPtr->weakAuthorPtr = authorPtr;
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authorPtr->weakBookPtr = bookPtr;
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// set the shared_ptr data members to create the memory leak
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bookPtr->sharedAuthorPtr = authorPtr;
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authorPtr->sharedBookPtr = bookPtr;
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// reference count for bookPtr and authorPtr is two
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std::cout << fmt::format("Reference count for Book {} is {}\n",
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bookPtr->title, bookPtr.use_count());
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std::cout << fmt::format("Reference count for Author {} is {}\n\n",
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authorPtr->name, authorPtr.use_count());
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// access the cross references to print the data they point to
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std::cout << "Access Author name and Book title via weak_ptrs:\n";
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bookPtr->printAuthorName();
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std::cout << "\n";
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authorPtr->printBookTitle();
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// reference count for each shared_ptr is two
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std::cout << fmt::format("\nReference count for Book {} is {}\n",
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bookPtr->title, bookPtr.use_count());
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std::cout << fmt::format("Reference count for Author {} is {}\n\n",
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authorPtr->name, authorPtr.use_count());
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// the shared_ptrs go out of scope, the Book and Author are destroyed
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std::cout << "End of main. shared_ptrs going out of scope.\n";
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}
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/**************************************************************************
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* (C) Copyright 1992-2022 by Deitel & Associates, Inc. and *
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* Pearson Education, Inc. All Rights Reserved. *
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* *
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* DISCLAIMER: The authors and publisher of this book have used their *
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* best efforts in preparing the book. These efforts include the *
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* development, research, and testing of the theories and programs *
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* to determine their effectiveness. The authors and publisher make *
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* no warranty of any kind, expressed or implied, with regard to these *
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* programs or to the documentation contained in these books. The authors *
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* and publisher shall not be liable in any event for incidental or *
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* consequential damages in connection with, or arising out of, the *
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* furnishing, performance, or use of these programs. *
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**************************************************************************/
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