Function that instantiates several objects at once-CodePudding

I'm making a simple game that has several item objects belonging to the same class. Instead of filling my main function with a never-ending list of objects, I wanted to create a function that does that and then call it at the beginning of the main function, but I realized that they get destroyed once their function ends, like normal variables. Is there a workaround to instantiate all the objects without writing a huge list inside my main function? (The following code isn't the one I am using in my program, it is simplified)

#include <iostream>

class Items
{
    public:
    std::string name;
    int number;
};

void CreateObjects()
{
    Items obj1 = {"Obj1", 1};
    Items obj2 = {"Obj2", 2};
    Items obj3 = {"Obj3", 3};
}

int main ()
{
    CreateObjects();
    std::cout << obj1.name;
    //here I get an error saying "Identifier obj1 is undefined"
}

CodePudding user response：

class Items
{
    public:
    std::string name;
    int number;
};

You declared a class with these variables. Great, let's now create another class with three of these items:

class Objects {

public:

    Items obj1, obj2, obj3;

    Objects() : obj1{"Obj1", 1},
                obj2{"Obj2", 2},
                obj3{"Obj3", 3}
    {
    }
};

Mission accomplished, you don't even need a separate function! Just instantiate an Objects class in your main, as a local variable, and you're done:

Objects objects;

std::cout << objects.obj1.name;

CodePudding user response：

obj1 is not in the scope of the function you're using it. This is a very fundamental concept for languages from the C/C /Java/JS/F#/… range of programming languages: Variables aren't accessible from outside the {} they were defined in (their scope). In your case, at the point you're trying to access them, they don't even exist anymore: all three obj1/2/3 were destroyed at the end of CreateObjects.

So, in your use case, you'd probably write this completely different¹. But you can do things like

#include <iostream>
#include <string>
#include <tuple>
class Item {
public:
  std::string name;
  int number;
};

auto createStuff() {
  Item obj1{"Obj1", 1};
  Item obj2{"Obj2", 2};
  Item obj3{"Obj3", 2};
  return std::tie(obj1, obj2, obj3); 
}

int main() {
  auto [a,b,c] = createStuff();
  std::cout << "a: " << a.name << " b: " << b.name << " c: " << c.name << "\n";
}

¹ (obsoleted by edit)