Friend class
suggest changeA whole class may be declared as friend. Friend class declaration means that any member of the friend may access private and protected members of the declaring class:
class Accesser {
public:
void private_accesser1();
void private_accesser2();
};
class PrivateHolder {
public:
PrivateHolder(int val) : private_value(val) {}
friend class Accesser;
private:
int private_value;
};
void Accesser::private_accesser1() {
PrivateHolder ph(10);
// OK.
std::cout << ph.private_value << std::endl;
}
void Accesser::private_accesser2() {
PrivateHolder ph(10);
// OK.
std::cout << ph.private_value + 1 << std::endl;
}
Friend class declaration is not reflexive. If classes need private access in both directions, both of them need friend declarations.
class Accesser {
public:
void private_accesser1();
void private_accesser2();
private:
int private_value = 0;
};
class PrivateHolder {
public:
PrivateHolder(int val) : private_value(val) {}
// Accesser is a friend of PrivateHolder
friend class Accesser;
void reverse_accesse() {
// but PrivateHolder cannot access Accesser's members.
Accesser a;
std::cout << a.private_value;
}
private:
int private_value;
};
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