47 lines
1.9 KiB
C++
47 lines
1.9 KiB
C++
// fig09_28.cpp
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// Friends can access private members of a class.
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#include <fmt/format.h>
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#include <iostream>
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#include "fmt/format.h" // In C++20, this will be #include <format>
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// Count class definition
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class Count {
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friend void setX(Count& c, int value); // friend declaration
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public:
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int getX() const { return m_x; }
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private:
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int m_x{0};
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};
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// function modifyX can modify private data of Count
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// because modifyX is declared as a friend of Count (line 8)
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void modifyX(Count& c, int value) {
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c.m_x = value; // allowed because modifyX is a friend of Count
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}
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int main() {
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Count counter{}; // create Count object
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std::cout << fmt::format("Initial counter.m_x: {}\n", counter.getX());
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modifyX(counter, 8); // change x's value using a friend function
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std::cout << fmt::format("counter.m_x after modifyX: {}\n",
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counter.getX());
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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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**************************************************************************/ |