I recently had a test on class inheritance and one of the questions required me to write a program that had a function in the parent class that required a private variable from the child class to work. This is what the question asked:
"Write a program that consists of two classes. A parent class, Human, and a child class, Student. (You may use a different human if needed, IE : ‘Baby’ class instead of ‘Student) Create a public inheritance connection between both classes.
The parent class should have the following member functions PUBLIC sleep() - prints a message about the hours slept and quits program
The child class have the following members functions and variables : PUBLIC setHoursSlept() - lets user input amount of hours slept. PRIVATE getHoursSlept() - returns amount of hours sleep. PRIVATE hoursSlept - variable that accepts the amount of hours slept."
I had no idea how to make hoursSlept accessable from the parent class So here is what I submitted
#include <iostream>
using namespace std;
class Human{
public:
//taking the L on this one
//defaults hours slept to 0
int hoursSlept=0;
//ends the program
void sleep(){
cout << "I slept " << hoursSlept << " hours" << endl;
exit(0);
}
};
//make a child class of human with a public connection called student
class Student: public Human{
public:
void setHoursSlept(){
cout << "enter hours slept" << endl;
cin >> hoursSlept;
}
private:
int getHoursSlept(){
return hoursSlept;
}
};
int main() {
//make new student
Student test;
//set hours slept
test.setHoursSlept();
//sleep
test.sleep();
}
CodePudding user response：
I think the composer of the test <expletive deleted>ed up. There are ways to hack around the protections built into C , but they tend to be brittle. Here's one hack that's not brittle and takes advantage of the fact that the accessibility of a function takes no part in the resolution of overrides.
#include <iostream>
using namespace std;
class Human
{
public:
virtual int getHoursSlept() = 0; // can now call getHoursSlept in derived classes
// regardless of accessibility
void sleep()
{
cout << "I slept " << getHoursSlept() << " hours" << endl;
exit(0);
}
};
class Student: public Human
{
int hoursSlept = 0;
public:
void setHoursSlept()
{
cout << "enter hours slept" << endl;
cin >> hoursSlept;
}
private:
int getHoursSlept() override
{
return hoursSlept;
}
};
int main()
{
//make new student
Student test;
//set hours slept
test.setHoursSlept();
//sleep
test.sleep();
}