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C++ Access Specifiers
Public Access Specifier:
Public members are accessible from outside the class. They can be accessed directly using an object of the class.
class MyClass {
public:
int myNumber;
};
int main() {
MyClass obj;
obj.myNumber = 15;
return 0;
}
Explanation:
Here, myNumber is a public member of MyClass, thus it can be accessed and modified directly using an object of MyClass.
Private Access Specifier
Private Access Specifier:
Private members cannot be accessed, or even viewed from outside the class. Only the class's own methods can access these members.
class MyClass {
private:
int myNumber;
public:
void setNumber(int n) {
myNumber = n;
}
int getNumber() {
return myNumber;
}
};
int main() {
MyClass obj;
obj.setNumber(15);
return obj.getNumber();
}
Explanation:
Here, myNumber is a private member of MyClass, so it can only be accessed or modified through the public methods setNumber and getNumber.
Protected Access Specifier
Protected Access Specifier:
Protected members are similar to private, but they can also be accessed in derived classes.
class Base {
protected:
int myNumber;
};
class Derived : public Base {
public:
void setNumber(int n) {
myNumber = n;
}
int getNumber() {
return myNumber;
}
};
int main() {
Derived obj;
obj.setNumber(15);
return obj.getNumber();
}
Explanation:
Here, myNumber is a protected member of Base, allowing it to be accessed in the Derived class.
Default Access Specifier
Default Access Specifier:
In C++, the default access specifier for members of a class is private.
class MyClass {
int myNumber; // private by default
public:
void setNumber(int n) {
myNumber = n;
}
int getNumber() {
return myNumber;
}
};
int main() {
MyClass obj;
obj.setNumber(15);
return obj.getNumber();
}
Explanation:
Without specifying, myNumber is private by default, and it requires public methods to access or modify it.
Friend Function
Friend Function:
A friend function can access private and protected members of a class in which it is declared as a friend.
class MyClass {
private:
int myNumber;
public:
MyClass() : myNumber(0) {}
friend void setNumber(MyClass &obj, int n);
};
void setNumber(MyClass &obj, int n) {
obj.myNumber = n;
}
int main() {
MyClass obj;
setNumber(obj, 15);
return 0;
}
Explanation:
The function setNumber is a friend of MyClass and can access its private members directly.
Friend Class
Friend Class:
A friend class can access private and protected members of another class in which it is declared as a friend.
class MyClass {
private:
int myNumber;
public:
MyClass() : myNumber(0) {}
friend class FriendClass;
};
class FriendClass {
public:
void setNumber(MyClass &obj, int n) {
obj.myNumber = n;
}
};
int main() {
MyClass obj;
FriendClass fObj;
fObj.setNumber(obj, 15);
return 0;
}
Explanation:
FriendClass is a friend of MyClass and can access its private members directly.
Using Public Inheritance
Public Inheritance:
In public inheritance, public members of the base class become public in the derived class, while protected members remain protected.
class Base {
public:
int publicVar;
protected:
int protectedVar;
};
class Derived : public Base {
public:
void setVars(int pub, int prot) {
publicVar = pub;
protectedVar = prot;
}
};
int main() {
Derived obj;
obj.setVars(10, 20);
return 0;
}
Explanation:
Derived class can access public and protected members of the Base class, but not private members.
Using Protected Inheritance
Protected Inheritance:
In protected inheritance, both public and protected members of the base class become protected in the derived class.
class Base {
public:
int publicVar;
protected:
int protectedVar;
};
class Derived : protected Base {
public:
void setVars(int pub, int prot) {
publicVar = pub;
protectedVar = prot;
}
};
int main() {
Derived obj;
// obj.publicVar = 10; // Error: publicVar is protected in Derived
obj.setVars(10, 20);
return 0;
}
Explanation:
In this case, publicVar is not directly accessible from outside the Derived class since it becomes protected.
Using Private Inheritance
Private Inheritance:
In private inheritance, both public and protected members of the base class become private in the derived class.
class Base {
public:
int publicVar;
protected:
int protectedVar;
};
class Derived : private Base {
public:
void setVars(int pub, int prot) {
publicVar = pub;
protectedVar = prot;
}
};
int main() {
Derived obj;
// obj.publicVar = 10; // Error: publicVar is private in Derived
obj.setVars(10, 20);
return 0;
}
Explanation:
In this scenario, publicVar and protectedVar are private in Derived and cannot be accessed directly from outside.
Access Specifiers in Struct
Access Specifiers in Struct:
In C++, members of a struct are public by default, unlike a class where they are private by default.
struct MyStruct {
int myNumber; // public by default
};
int main() {
MyStruct obj;
obj.myNumber = 15;
return obj.myNumber;
}
Explanation:
Here, myNumber is public by default in MyStruct, allowing direct access and modification.
