How to declare a global object in a switch statement - c++

Question

I am having a problem, where I need to declare an object for a class based on user input. The problem is that the scope of the object is stuck in the switch statement, and I was wondering if there was a way to make it public.
//ask the user to choose the class of the first fighter
cout << "Welcome to the fighting arena! Would you like the first competitor to be a FIGHTER <1>, a WIZARD <2>, a ROGUE <3>, or a RANGER <4>?" << endl;
cin >> competitor1;
cout << "And what is the name of the competitor?" << endl;
cin >> name1;
//creates an object in the appropriate class and initializes it
switch (competitor1)
{
case 1:
{
Fighter Battler1(name1);
break;
}
case 2:
{
Wizard Battler1(name1);
break;
}
case 3:
{
Rogue Battler1(name1);
break;
}
case 4:
{
Ranger Battler1(name1);
break;
}
default:
cout << "Sorry please enter a valid number!" <<endl << endl;
break;
}
cout << Battler1.hp //this is undefined because of the scope
Yes everything is written inside the main fuction, I know the probelm is scope and just need a way to get around it.

Answer 1

I wouldn't use a switch case at all here, instead, an array of functors, that each create a different type of fighter and return a pointer to their base, i.e.
template<typename T>
std::unique_ptr<Champion> Create( ) { return std::make_unique<T>( ); }
std::function<std::unique_ptr<Champion>(void)> createFunctions [] = {
Create<Fighter>
,Create<Rogue>
,Create<Wizard>
,Create<Ranger>
};
Usage:
std::cin >> competitor1;
std::unique_ptr<Champion> Battler1 = createFunctions[competitor1];
std::cout << Battler1->hp;

Answer 2

You cannot do it as you described. You will need some kind of polymorphism: an object that will change it's behavior depending on it's type.
The most straightforward way to do it would be to use a variant:
using Battler = std::variant<Fighter, Wizard, Rogue, Ranger>;
auto battler1 = [&]() -> std::optional<Battler> {
switch (competitor1)
{
case 1:
return Fighter{name1};
case 2:
return Wizard{name1};
case 3:
return Rogue{name1};
case 4:
return Ranger{name1};
default:
cout <<"Sorry please enter a valid number!" << endl;
return std::nullopt;
}
}();
// if a valid number has been chose.
if (battler1) {
cout << std::visit([](auto& battler) { return battler.hp; }, *battler1);
}
Note that you need an up to date compiler, or using boost::variant instead. This solution might also not be the most scalable as you'll need to effectively update the Battler alias when adding a new battler type.
Also, you could use polymorphism through pointers and vtables. It require more changes to your program, but might be more appropriate in some cases:
struct Battler {
virtual int getHp() const = 0;
virtual ~Battler() = default;
};
struct Fighter : Battler {
int getHp() const override {
return hp;
}
};
struct Wizard : Battler {
int getHp() const override {
return hp;
}
};
// ... all other classes of Battler
Then, change you switch case accordingly:
std::unique_ptr<Battler> battler1;
switch (competitor1)
{
case 1:
battler1 = std::make_unique<Fighter>(name1);
break;
case 2:
battler1 = std::make_unique<Wizard>(name1);
break;
case 3:
battler1 = std::make_unique<Rogue>(name1);
break;
case 4:
battler1 = std::make_unique<Ranger>(name1);
break;
default:
cout << "Sorry please enter a valid number!" <<endl << endl;
break;
}
// if a valid number has been chose
if (battler1) {
cout << battler1->getHp();
}

Answer 3

If you could make the object (Battler1) global, what datatype would it be? Instance of class Fighter, Wizard, Rogue or Ranger?
The solution to your problem is this: Create a parent class (let's say, Character) from which all the others (Fighter...) will inherit: class Fighter : Character etc. And then, create the objects dynamically:
Character *battler;
switch (...) {
case 1:
battler = new Fighter(name);
break;
case 2:
battler = new Wizard(name);
break;
}
// don't forget to free the memory when not needed anymore
delete battler;