Functions and Objects
Friend Function in C++
Friend functions can access private and protected members of a class object passed into the function.
Syntax
//within class declaration
class className {
friend functionDeclaration(passedParameters){
}
}
//function definition, outside of class
functionDeclaration(passedParameters){
//suppose classObject is a className object passed in as a parameter
//private and protected members of classObject can be accessed directly
classObject.privateMember = value;
//in addition, newly created objects can also have their private/protected members accessed
}
Notes
Function declaration for a friend function is similar to that of a regular function, but with the 'friend' keyword.
Friend functions actually are not a member of any class.
Example
class Car {
public:
friend double kphSpeed(const Car) const{}
private:
double mph;
}
double kphSpeed(const Car c) const {
double kph = c.mph * 1.60934; //function can access private mph directly
return kph;
}
