C++ Tutorial/Function/reference parameter — различия между версиями
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Версия 14:21, 25 мая 2010
Содержание
Pass by reference by using pointer
#include <iostream>
void swap(int *x, int *y);
int main()
{
int x = 5, y = 10;
std::cout << "Main. Before swap, x: " << x << " y: " << y << "\n";
swap(&x,&y);
std::cout << "Main. After swap, x: " << x << " y: " << y << "\n";
return 0;
}
void swap (int *px, int *py)
{
int temp;
std::cout << "Swap. Before swap, *px: " << *px << " *py: " << *py << "\n";
temp = *px;
*px = *py;
*py = temp;
std::cout << "Swap. After swap, *px: " << *px << " *py: " << *py << "\n";
}Main. Before swap, x: 5 y: 10 Swap. Before swap, *px: 5 *py: 10 Swap. After swap, *px: 10 *py: 5 Main. After swap, x: 10 y: 5
Pass by reference using references
#include <iostream>
void swap(int &x, int &y);
int main()
{
int x = 5, y = 10;
std::cout << "Main. Before swap, x: " << x
<< " y: " << y << "\n";
swap(x,y);
std::cout << "Main. After swap, x: " << x
<< " y: " << y << "\n";
return 0;
}
void swap (int &rx, int &ry)
{
int temp;
std::cout << "Swap. Before swap, rx: " << rx
<< " ry: " << ry << "\n";
temp = rx;
rx = ry;
ry = temp;
std::cout << "Swap. After swap, rx: " << rx
<< " ry: " << ry << "\n";
}Main. Before swap, x: 5 y: 10 Swap. Before swap, rx: 5 ry: 10 Swap. After swap, rx: 10 ry: 5 Main. After swap, x: 10 y: 5
Passing references to objects
#include <iostream>
class MyClass
{
public:
MyClass();
MyClass(MyClass&);
~MyClass();
int GetAge() const { return itsAge; }
void SetAge(int age) { itsAge = age; }
private:
int itsAge;
};
MyClass::MyClass()
{
std::cout << "Simple Cat Constructor...\n";
itsAge = 1;
}
MyClass::MyClass(MyClass&)
{
std::cout << "Simple Cat Copy Constructor...\n";
}
MyClass::~MyClass()
{
std::cout << "Simple Cat Destructor...\n";
}
const MyClass & f (const MyClass & obj);
int main()
{
MyClass myObject;
std::cout << "myObject is " << myObject.GetAge() << " years old\n";
int age = 5;
myObject.SetAge(age);
std::cout << "myObject is " << myObject.GetAge() << " years old\n";
std::cout << "Calling f...\n";
f(myObject);
std::cout << "myObject is " << myObject.GetAge() << " years old\n";
return 0;
}
const MyClass & f (const MyClass & obj)
{
std::cout << "Function Two. Returning...\n";
std::cout << "myObject is now " << obj.GetAge()<< " years old \n";
return obj;
}Simple Cat Constructor... myObject is 1 years old myObject is 5 years old Calling f... Function Two. Returning... myObject is now 5 years old myObject is 5 years old Simple Cat Destructor...
Returning multiple values from a function using references
#include <iostream>
void f(int, int&, int&);
int main()
{
int number = 2, squared, cubed;
f(number, squared, cubed);
std::cout << "number: " << number << "\n";
std::cout << "square: " << squared << "\n";
std::cout << "cubed: " << cubed << "\n";
return 0;
}
void f(int n, int &rSquared, int &rCubed)
{
rSquared = n*n;
rCubed = n*n*n;
}number: 2 square: 4 cubed: 8
Use reference parameters to create the swap() function.
#include <iostream>
using namespace std;
void swap(int &x, int &y);
int main()
{
int i, j;
i = 10;
j = 20;
cout << "Initial values of i and j: ";
cout << i << " " << j << "\n";
swap(j, i);
cout << "Swapped values of i and j: ";
cout << i << " " << j << "\n";
return 0;
}
void swap(int &x, int &y)
{
int temp;
temp = x;
x = y;
y = temp;
}Initial values of i and j: 10 20 Swapped values of i and j: 20 10
Using a reference parameter.
#include <iostream>
using namespace std;
void f(int &i); // i is a reference parameter
int main()
{
int val = 1;
cout << "Old value for val: " << val << "\n";
f(val);
cout << "New value for val: " << val << "\n";
return 0;
}
void f(int &i)
{
i = 10;
}Old value for val: 1 New value for val: 10
