类访问推送中的STL向量

Question

What is the syntax to push integer into vector, which is inside Custothe class?

class Customer {
vector <int> loyalID;
}

int main {
Customer customer;

vector<Customer>customers;

customers.push_back(/*some integers to go into loyalID vector*/);
}

Answer 1

Either make the vector public (which is not recommended) or write a public member function in the class:

void Customer::push_back(int i)
{
    loyalID.push_back(i);
}

In main once you have elements in customers you could write something like this:

customers[0].push_back(10);

Answer 2

loyalID is a private field of Customer . Either make it public (not recommended), or add a public method:

class Customer {
  vector <int> loyalID;

  public:
  void addLoyalId(int id)
  {
    loyalID.push_back(id);
  }
}

Accessing loyal ids:

class Customer {
  vector <int> loyalID;

  public:
  void addLoyalId(int id)
  {
    loyalID.push_back(id);
  }

  std::vector<int>::iterator begin() const { return _loyalID.begin(); }
  std::vector<int>::iterator end() const { return _loyalID.end(); }
}

Usage:

Customer c;
c.addLoyalId(1);
c.addLoyalId(2);
c.addLoyalId(3);

for (auto&& id : c)
{
  std::cout << id << " ";
} // will print "1 2 3"