Error using unique_ptr to access functions in subclasses - c++

Question

My aim with this program is to have a vector of objects describing various types of vehicles. The base class will have a user defined type variable, while each of the subclasses will have a default value as type(eg Van, Bus, etc.). After some searching I found that the best way to use both base and derived classes in a vector is to use a vector of pointers. Here is a simplified version of the code I wrote:
#include <iostream>
#include <string>
#include <vector>
#include <memory>
using namespace std;
class Vehicle
{
public:
Vehicle();
~Vehicle();
virtual void Initialize(string a,string b, int c, int d, int e, string f);
void print_details();
void get_yard(int x);
string type;
protected:
string make_and_model;
int max_pass;
int max_load;
int yard;
string date;
};
class Lorry : public Vehicle
{
public:
void Initialize(string a="Lorry", string b, int c, int d, int e, string f);
};
int i,count;
std::vector<std::unique_ptr<Vehicle>> arr;
Vehicle::Vehicle()
{
std::cout << "New Entry created." << std::endl;
}
Vehicle::~Vehicle()
{
std::cout << "Entry closed." << std::endl;
}
void Vehicle::Initialize(string a,string b, int c, int d, int e, string f)
{
type=a;
make_and_model=b;
max_pass=c;
max_load=d;
yard=e;
date=f;
}
void Lorry::Initialize(string a="Lorry", string b, int c, int d, int e, string f)
{
make_and_model=b;
max_pass=c;
max_load=d;
yard=e;
date=f;
}
void Vehicle::print_details()
{
std::cout << "Vehicle Type:"<< type << std::endl;
std::cout << "Make And Model:"<< make_and_model << std::endl;
std::cout << "Maximum Passengers:"<< max_pass << std::endl;
std::cout << "Maximum Load Capacity(in Kg):"<< max_load << std::endl;
std::cout << "Located Yard:"<< yard << std::endl;
std::cout << "Date of Arrival(dd-MM-YYYY):"<< date <<"\n"<< std::endl;
}
void new_objects()
{
std::cout<<"How many entries?"<<std::endl;
std::cin>>count;
std:: cout<<"The open yards are: Yard 1, Yard 2, Yard 3"<<std::endl;
for (i = 0; i < count; i++)
{
int vc_choice;
std::cout<<"What is the vehicle type?"<<std::endl;
std::cout<<"1.Lorry\n6.Other\n";
std::cin>>vc_choice;
string a;
string b;
int c;
int d;
int e;
string f;
switch (vc_choice)
{
case 1:
arr.emplace_back(new Lorry());
std::cout<<"Enter the vehicle make and model: "<<std::endl;
std::cout << "WARNING: Do NOT use spaces, use underscores." << std::endl;
std::cin>>b;
std::cin.clear();
std::cout<<"Enter the maximum passenger capacity: "<< std::endl;
std::cin>>c;
std::cin.clear();
std::cout<<"Enter the maximum load capacity(Kgs): "<<std::endl;
std::cin>>d;
std::cout<<"Enter the yard number"<<std::endl;
std::cin>>e;
std::cout<<"Enter the date of arrival(dd-mm-yyyy): "<<std::endl;
std::cin>>f;
arr.Initialize(a,b,c,d,e,f);
break;
default:
arr.emplace_back(new Vehicle());
std::cout<<"Enter the vehicle type: "<<std::endl;
std::cout << "WARNING: Do NOT use spaces, use underscores." << std::endl;
std::cin>>a;
std::cout<<"Enter the vehicle make and model: "<<std::endl;
std::cout << "WARNING: Do NOT use spaces, use underscores." << std::endl;
std::cin>>b;
std::cin.clear();
std::cout<<"Enter the maximum passenger capacity: "<< std::endl;
std::cin>>c;
std::cin.clear();
std::cout<<"Enter the maximum load capacity(Kgs): "<<std::endl;
std::cin>>d;
std::cout<<"Enter the yard number"<<std::endl;
std::cin>>e;
std::cout<<"Enter the date of arrival(dd-mm-yyyy): "<<std::endl;
std::cin>>f;
arr.Initialize(a,b,c,d,e,f));
break;
}
}
}
void print_all()
{
for (int a= 0; a<5; i++)
{
arr[a].print_details();
}
}
int main()
{
new_objects();
print_all();
return 0;
}
Trying to compile it I get this error:
[test unique_ptr.cpp 2021-04-24 06:59:33.521]
,,test unique_ptr.cpp: In function 'void new_objects()':
test unique_ptr.cpp:122:29: error: 'class std::vector<std::unique_ptr<Vehicle> >' has no member named
'Initialize'
122 | arr.Initialize(a,b,c,d,e,f);
| ^~~~~~~~~~
test unique_ptr.cpp:151:29: error: 'class std::vector<std::unique_ptr<Vehicle> >' has no member named
'Initialize'
151 | arr.Initialize(a,b,c,d,e,f));
| ^~~~~~~~~~
test unique_ptr.cpp: In function 'void print_all()':
test unique_ptr.cpp:162:16: error: '__gnu_cxx::__alloc_traits<std::allocator<std::unique_ptr<Vehicle> >,
std::unique_ptr<Vehicle> >::value_type' {aka 'class std::unique_ptr<Vehicle>'} has no member named
'print_details'
162 | arr[a].print_details();
| ^~~~~~~~~~~~~
I've tried using the arrow operator but this still doesn't work, as arr is not a pointer. How can I get the program to run?

Answer 1

Three types of errors.
You can't use default value for the 1st argument and leaving the rest alone. Meaning you cannot write void Initialize(string a="Lorry", string b, int c, int d, int e, string f);. You can write:
void Initialize(string a, string b, int c, int d, int e, string f)
or
void Initialize(string a, string b, int c, int d, int e, string f="Lorry")
or
void Initialize(string a, string b, int c, int d, int e = 0, string f="Lorry")
& the second one is you can't use . to access the method from a pointer, instead you need to use ->. read the thread. The third one is you are calling Initialize from a vector. You need to specify the index to indicate its element. You need to write:
arr[arr.size() - 1]->Initialize(a, b, c, d, e, f);
......
arr[a]->print_details();