What Is Friend Function in Data Structure?
In data structure, a friend function is a special type of function that is allowed to access private and protected members of a class. It is declared inside the class but defined outside of it. The friend function can be used to access private member variables and functions of a class, even though it is not a member of that class.
Why Use Friend Functions?
Friend functions are useful in situations where you need to access private or protected members of a class from outside the class scope. They provide an alternative to making all the members public or creating getter and setter methods for every private member. By declaring a function as a friend, you can give that function special privileges to access the private data of a class.
How to Declare a Friend Function?
To declare a friend function in C++, you need to use the friend keyword followed by the function declaration inside the class definition. Here’s an example:
class MyClass {
// Declare friend function
friend void myFriendFunction();
};
The friend keyword indicates that myFriendFunction() has access to all private and protected members of MyClass.
Defining a Friend Function
To define the friend function, you need to write its implementation outside the class definition. Here’s an example:
class MyClass {
// Declare friend function
friend void myFriendFunction();
};
// Define friend function
void myFriendFunction() {
// Access private members of MyClass here
}
Accessing Private Members with Friend Functions
Once you have declared and defined a friend function, you can use it to access private members of the class. Here’s an example:
class MyClass {
private:
int privateData;
public:
MyClass(int data) : privateData(data) {}
// Declare friend function
friend void myFriendFunction();
};
// Define friend function
void myFriendFunction() {
MyClass obj(10);
cout << "Private data accessed via friend function: " << obj.privateData << endl;
}
In the above example, myFriendFunction() is able to access the privateData member variable of MyClass, even though it is not a member of MyClass.
Limitations of Friend Functions
While friend functions can be useful in certain situations, it is important to use them judiciously. Here are some limitations to consider:
- Friend functions break encapsulation and can potentially lead to less maintainable code if used excessively.
- They are not inherited by derived classes. A friend function declared in a base class does not automatically become a friend of any derived classes.
- Friend functions cannot be declared as const or volatile.
Conclusion
In summary, a friend function in data structure is a special type of function that has access to the private and protected members of a class. It provides an alternative way to access private data without compromising encapsulation. However, it should be used judiciously considering its limitations and potential impact on code maintainability.