evil.cpp

#include <iostream>

using namespace std;

class Bar {
    public:
        Bar(int a, int b): a(a), b(b) {};
        
        // a is mutable property, b isn't – by the contract of object's public interface
        void setA(int _a) { a = _a; }
    
        int getA() { return a; }
        int getB() { return b; }
    
    private:
        int a;
        int b;
};

// fak em all, look brah what i'm cooking here
class CrazyBarByFoo: public Bar {
    public:
        CrazyBarByFoo(): Bar(0, 0) {}
    
        int getA() { return 404; }
        
        // the number of the Beast, cause im craaaaaazeeeeeeyyy!
        int getB() { return 666; }
    private:
        using Bar::getA;
        using Bar::getB;
};


class Foo {
    public:
        explicit Foo(Bar &bar): bar(bar) {} 

        void prettyPleaseTalkWithBar1() {
            // yea, Foo is a good boi - using Bar's public interface as it should be
            bar.setA(7);
        }
        
        void prettyPleaseTalkWithBar2() {
            // boooooo, Foo is a nasty bastard, it is replacing Bar it was given by entirely different Bar!
            Bar barReplacement{69, 69}; // yea, im feeling nasty
            bar = barReplacement;
        }        

        void prettyPleaseTalkWithBar3() {
            // praise the Satan, muahaahahhaahahahaa!
            CrazyBarByFoo crazyBar;
            bar = crazyBar;
        }

    private:
        Bar &bar;
};

int main()
{
    Bar outsideBar{2, 3};
    Foo foo{outsideBar};
   
    // I gave you a Bar, so be kind and talk with it
    // [a Bar will be willing to talk if you speak its public interface ofc]
    foo.prettyPleaseTalkWithBar1();
   
    cout << outsideBar.getA() << endl; // cool, you talked with Bar and it changed its "a" to 7 - how nice!
    cout << outsideBar.getB() << endl; // "b" is still 3 – as it was given to Bar by its birthright
   
    // hey guys, lets talk again! keep the good communication comming :-)
    foo.prettyPleaseTalkWithBar2();
   
    cout << outsideBar.getA() << endl; // haha, very funny, after u talked Bar changed its "a" to 69 <3
    cout << outsideBar.getB() << endl; // DA FAK! what has happened in here?! did you kill my Bar and think I woudn't notice?!
   
    // ok, you have one more change, please don't be a disappointment
    foo.prettyPleaseTalkWithBar3();
   
    // now it got interesting: getA and getB are called upon the Bar class, not from the CrazyBarByFoo class
    // not bad after all – CPP could be much more EVIL :P
    // …unless…
    // …unless it can still be much more evil, but im still too much of a noobie to make it evil :P
    cout << outsideBar.getA() << endl;
    cout << outsideBar.getB() << endl;
   
    return 0;
}

gistfile1.txt

todo:
https://www.geeksforgeeks.org/copy-constructor-vs-assignment-operator-in-c/

im a noob getting roasted:
https://discord.com/channels/583251190591258624/742849025191051326/997845160723488808