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Non-friend/non-member functions cannot access private data of a class
#include <iostream>
using std::cout;
using std::endl;
class MyClass
{
public:
MyClass() : x( 0 )
{
}
void print() const
{
cout << x << endl;
}
private:
int x;
};
void cannotSetX( MyClass &c, int val )
{
//c.x = val; // ERROR: cannot access private member in MyClass
}
int main()
{
MyClass counter;
cannotSetX( counter, 3 );
return 0;
}private by default
#include <iostream>
using namespace std;
class MyClass {
int i; // private by default
public:
int getI() { return i; }
void setI(int j) { i = j; }
};
int main()
{
MyClass s;
s.setI(10);
cout << s.getI();
return 0;
}10
private fields
#include <iostream>
using namespace std;
struct MyClass {
int getI() { return i; } // these are public by default
void setI(int j) { i = j; }
private:
int i;
};
int main()
{
MyClass s;
s.setI(10);
cout << s.getI();
return 0;
}10
Using a class with private data members
#include <iostream>
#include <iostream>
using std::cout;
using std::endl;
class Box {
public:
Box(double lvalue, double wvalue, double hvalue) :length(lvalue), width(wvalue), height(hvalue) {
cout << "Box constructor called" << endl;
}
Box() {
cout << "Default constructor called" << endl;
length = width = height = 1.0; // Default dimensions
}
double volume() {
return length * width * height;
}
private:
double length;
double width;
double height;
};
int main() {
cout << endl;
Box firstBox(2.2, 1.1, 0.5);
Box secondBox;
Box* pthirdBox = new Box(15.0, 20.0, 8.0);
cout << firstBox.volume()<< endl;
cout << secondBox.volume()<< endl;
cout << pthirdBox->volume()<< endl;
delete pthirdBox;
return 0;
}Box constructor called
Default constructor called
Box constructor called
1.21
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