An introduction to the C++ programming language for game engine development.

2. Copy
Move
‫کردن‬ ‫فعال‬ ‫غیر‬Copy‫و‬Move

3. 01. void test(complex z1)
02. {
03. complex z2(z1); // Copy initialization
04. complex z3;
05. z3 = z2; // Copy assignment
06. // ...
07. }

4. 01. void bad_copy(Vector v1)
02. {
03. Vector v2 = v1; // Copy v1's representation into v2
04. v1[0] = 2; // v2[0] is now also 2!
05. v2[1] = 3; // v1[1] is now also 3!
06. }

5. 01. class Vector {
02. private:
03. // elem points to an array of sz doubles
04. double* elem;
05. int sz;
06. public:
07. Vector(int s); // Constructor
08. ~Vector() { delete[] elem; } // Destructor
09.
10. Vector(const Vector& a); // Copy constructor
11. Vector& operator=(const Vector& a); // Copy assignment
12.
13. double& operator[](int i);
14. const double& operator[](int i) const;
15. int size() const;
16. };

6. 01. Vector::Vector(const Vector& a) // Copy constructor
02. : elem(new double[sz]) // Allocate space for elements
03. , sz(a.sz)
04. {
05. for (int i = 0; i != sz; ++i) // Copy elements
06. elem[i] = a.elem[i];
07. }

7. 01. // Copy assignment
02. Vector& vector::operator=(const Vector& a)
03. {
04. double* p = new double[a.sz];
05. for (int i = 0; i != a.sz; ++i)
06. p[i] = a.elem[i];
07. delete[] elem;
08. elem = p;
09. sz = a.sz;
10. return *this;
11. }

8. 01. Vector operator+(const Vector& a, const Vector& b)
02. {
03. if (a.size() != b.size())
04. throw Vector_size_mismatch();
05. Vector res(a.size());
06. for (int i = 0; i != a.size(); ++i)
07. res[i] = a[i] + b[i];
08. return res;
09. }
01. void f(const Vector& x, const Vector& y, const Vector& z)
02. {
03. Vector r;
04. // ...
05. r = x + y + z;
06. // ...
07. }

9. 01. class Vector {
02. // ...
03. Vector(const Vector& a); // Copy constructor
04. Vector& operator=(const Vector& a); // Copy assignment
05.
06. Vector(Vector&& a); // Move constructor
07. Vector& operator=(Vector&& a); // Move assignment
08. };
09.
10. Vector::Vector(Vector&& a)
11. : elem(a.elem) // "grab the elements" form a
12. , sz(a.sz)
13. {
14. a.elem = nullptr; // Now a has no elements
15. a.sz = 0;
16. }

10. 01. Vector f()
02. {
03. Vector x(1000);
04. Vector y(1000);
05. Vector z(1000);
06. // ...
07. z = x; // We get a copy
08. y = std::move(x); // We get a move
09. // ...
10. return z; // We get a move
11. }

11. 01. class Shape {
02. public:
03. // No copy operations
04. Shape(const Shape&) = delete;
05. Shape& operator=(const Shape&) = delete;
06.
07. // No move operations
08. Shape(Shape&&) = delete;
09. Shape& operator=(Shape&&) = delete;
10.
11. ~Shape();
12. // ...
13. };