


Detailed explanation of C++ friend functions: What is the role of friend functions in multiple inheritance?
Friend functions allow non-member functions to access private members and play a role in multiple inheritance, allowing derived class functions to access private members of the base class.
C Detailed explanation of friend functions: The role of friend functions in multiple inheritance
Introduction to friend functions
A friend function is a special function that is given access to private members without requiring an object of the class. It is often used to allow non-member functions to access private data.
Syntax:
class ClassName { ... // 类成员 friend FunctionName; };
The role of friend functions in multiple inheritance
In multiple inheritance, a derived class Data members and methods can be inherited from multiple base classes. If a function in a derived class needs to access a private member of the base class, the function can be declared as a friend function.
Practical case
Suppose we have a Base
class and a derived classDerived that inherits from
Base
:
class Base { private: int data; }; class Derived : public Base { public: void printData() { std::cout << data << std::endl; } friend void printData2(Derived& obj); };
Since data
is a private member of Base
, the printData()
function in Derived
There is no way to access it directly. Therefore, we declare the printData2()
function as a friend function of Derived
:
void printData2(Derived& obj) { std::cout << obj.data << std::endl; }
Now, printData2()
can access ## Private data
member in #Derived.
Usage:
int main() { Derived obj; obj.printData(); printData2(obj); }
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