Question

I am new to c++ programming and I have a basic issue, I want to create N objects, N is is actually a user input.

I am specific about having object names, say beam1, beam2,…,beamX.

2 quick things

1. Is it possible in C++ to create dynamic object as this?

2. if it is how do we do tht? I am pasting code for your refrence..

       #include "iostream"
       # include <conio.h>
       using namespace std;
   
       // Static member variable is defined outside the class..
       class beam {
       public:
       int length;
       };
   
       int main () 
       {
          int i=0, no_of_spans, j;
          cout<< "Design Of a Continous Beam \n1) No Of Spans : ";
          cin >> no_of_spans;
          for (i =0; i < no_of_spans; i++) {
            j = i;
            beam;
            cout << "Length of Beam" << j+1 << " is : ";
            cin >> beami.length;
          }
   
          cout << "\nPress any key to continue..\n";
          getch ();
       }
   

This is obviously a code with errors, its put up as an example to get the idea.

Answer 1

As has already been stated by others (Luchian, John, Component and Ed) you can use a std::vector and it will dynamically grow as necessary to store the number of beam objects required.

If you wish to refer to these objects later by name you could store them in a std::map, with the key of the map being the object name (e.g. beam1, beam2, beam3, …, beamX):

std::map<std::string, beam> beams;
for (int i = 0; i < no_of_spans; i++)
{
    j = i;
    beam beam;
    std::string beam_name("beam" + boost::lexical_cast<std::string>(i + 1));
    cout << "Length of " << beam_name << " is : ";
    cin >> beam.length;
    beams.insert(std::make_pair(beam_name, beam));
}

—

boost::lexical_cast<> is a mechanism for converting (in this case) an int to a std::string. There other ways to achieve this (using std::ostringstream for example).