New to C OOP, I recently learned about classes and objects. I created a straightforward class and menu-driven program that adds a temp object to a vector of movies. I have a quick question that I can't quite understand.

Am I just pushing multiple "temp" objects into the vector?

In my head i'm visualizing this as vector my_movies = {temp, temp, temp}; and continously adding 'temp' objects until the user is done. Is this the right way to picture it?

#include <iostream>
#include <vector>

using namespace std;

class Movie
{
  private:
    string name;
  public:
    string get_name() { return name; }
    void set_name(string n) { name = n; }
};

void menu() {
  cout << "1. Add movie" << endl;
  cout << "2. Show Movies" << endl;
  cout << "3. Quit" << endl;
}

int getChoice(int &choice) {
  cout << "Enter you choice: ";
  cin >> choice;
  return choice;
}

int main() {

  vector<Movie> my_movies;
  int choice = 0;
  string name;

  do {
    menu();
    getChoice(choice);
    switch (choice) {
      case 1: {
        Movie temp;
        cout << "Set user name: ";
        cin >> name;
        temp.set_name(name);
        my_movies.push_back(temp);
        break;
      }
      case 2: {
        for (auto &mv : my_movies)
          cout << mv << endl;
        break;
      }
    }

  } while (choice != 3);

  return 0;
}

CodePudding user response：

In your case, when you are calling push_back it will copy your "temp" object, which is a local object on the stack. It will be copied into a new object which is stored on the heap, held by the vector object. The vector will store these as an array internally (the default vector with the default allocator etc).

It's also possible to "move" the object (under C 11 and later), if you understand the difference, but doing push_back(std::move(temp)), which generally gives better performance. In your case it would avoid copying the string member "name", and move it instead, avoiding a new allocation for the string inside the Movie in the vector.

See here for more details on push_back

Appends the given element value to the end of the container.

1. The new element is initialized as a copy of value.

https://en.cppreference.com/w/cpp/container/vector/push_back

If you are just talking about the name of the movie, it will be what ever is entered from cin. Objects don't have names themselves. The local variable name "temp" is just what you see when you write the code, but is just used to tell the compiler which object is being used - the object itself doesn't have a name form the compilers perspective.