Create a vector of strings in one file and use it in another file

Question

I have long list of strings that I want to put define and declare in its own .h file. I want to group these strings into vectors, and use these values in a different .h file. The second file will std::find to see if a string is in the vector. Are vectors a good way group the strings to do this or should I use another method?

I have a kitBreakdown.h file will have multiple vectors of strings like the following:

    #ifndef KIT_BREAKDOWN_H
    #define KIT_BREAKDOWN_H
    #include <vector>

    void setup(){
        std::vector<std::string> Bricks_Plates;
        Bricks_Plates.push_back("2_1_plate");        //4211398
        Bricks_Plates.push_back("2_1_brick");        //4211388
        Bricks_Plates.push_back("2_2_brick");        //4211387
        Bricks_Plates.push_back("4_1_plate");        //4211445
        Bricks_Plates.push_back("4_2_plate");        //4211444
        Bricks_Plates.push_back("6_2_plate");        //4211542
        Bricks_Plates.push_back("8_2_plate");        //4211449
        Bricks_Plates.push_back("2_1_smooth_plate"); //4211052
    }
    #endif

I want to use these strings in a different file called searchControl.h, which contains a searchControl class to implement a robotic search.

    #include "kitBreakdown.h"
    #include <algorithm>


    // The purpose of this class is to implement a search control structure
// So individual variables can be set up (limbs and cameras) before hand
// Search Geometry should be set and checked to ensure valid choices are made
    class SearchControl
    { ...
    private:
    void _init_search();
    ...

    std::vector<std::string> Bricks_Plates;
    };

    void SearchControl::_init_search()
    {...
    std::cout<<"What is your Desired Piece Type?\n";
    int i = 0;
      while (i==0)
      {
      std::cin >> _desired_piece;
        if (std::find(Bricks_Plates.begin(),Bricks_Plates.end(), _desired_piece) !=Bricks_Plates.end()) 
        {
        std::cout << "Cool. " << _desired_piece << " will go in one bin and anything else will go in another\n";
        i=1;
        }
        else {
        std::cout << "I don't recognize what you want\n";
        std::cout << "Your Choices are...\n";
          for (int j=0; j<Bricks_Plates.size(); j++) {
          std::cout<< Bricks_Plates[j]<< "\n";
          }
        std::cout << "Enter a new Desired Piece Type:\n";
        }
      }
    }

I want this to ask for the _desired_piece, check if _desired_piece is in Brick_Plates vector, and carry out the if statement accordingly. However when I run this code it outputs no elements of the Brick_Plates vector. How can I pass the values of the strings in the first header file to the second one?

Take a look at http://stackoverflow.com/questions/1433204/how-do-i-share-a-variable-between-source-files-in-c-with-extern-but-how/1433387#1433387 — R Sahu, Jul 24 '14 at 17:41
Thanks! I'm still not sure I completely understand. I made a kitBreakdown.cpp file which defines the vector and includes kitBreakdown.h. kitBreakdown.h is only has the extern std::vector Bricks_Plates; line. I'm still getting an empty vector when I run. — tmwcheese, Jul 24 '14 at 18:33
Try to reduce the code to as few lines as possible that still produces the problem. Then post the code. — R Sahu, Jul 24 '14 at 18:35

score 1 · Accepted Answer · answered Jul 24 '14 at 18:38

Modify your steup function to return the vector which you built up:

#ifndef KIT_BREAKDOWN_H
#define KIT_BREAKDOWN_H
#include <vector>

std::vector<std::string> setup(){
    std::vector<std::string> Bricks_Plates;
    Bricks_Plates.push_back("2_1_plate");        //4211398
    Bricks_Plates.push_back("2_1_brick");        //4211388
    Bricks_Plates.push_back("2_2_brick");        //4211387
    Bricks_Plates.push_back("4_1_plate");        //4211445
    Bricks_Plates.push_back("4_2_plate");        //4211444
    Bricks_Plates.push_back("6_2_plate");        //4211542
    Bricks_Plates.push_back("8_2_plate");        //4211449
    Bricks_Plates.push_back("2_1_smooth_plate"); //4211052
    return Bricks_Plates;
}
#endif

and add a Constructor to SearchControl which initializes its member Bricks_Plates to the value which you return from setup:

#include "kitBreakdown.h"
#include <algorithm>

class SearchControl
{ ...
public:
    SearchControl():Bricks_Plates(setup()){}
private:
void _init_search();
...

std::vector<std::string> Bricks_Plates;
};

void SearchControl::_init_search()
{...
std::cout<<"What is your Desired Piece Type?\n";
int i = 0;
  while (i==0)
  {
  std::cin >> _desired_piece;
    if (std::find(Bricks_Plates.begin(),Bricks_Plates.end(), _desired_piece) !=Bricks_Plates.end()) 
    {
    std::cout << "Cool. " << _desired_piece << " will go in one bin and anything else will go in another\n";
    i=1;
    }
    else {
    std::cout << "I don't recognize what you want\n";
    std::cout << "Your Choices are...\n";
      for (int j=0; j<Bricks_Plates.size(); j++) {
      std::cout<< Bricks_Plates[j]<< "\n";
      }
    std::cout << "Enter a new Desired Piece Type:\n";
    }
  }
}

Although R Sahus comment is technically correct and using extern or global variables is sometimes the only way to do things it is widely considered bad style to use globals.

Great thanks! And if I have more vectors in addition to Bricks_Plates I could make a function for each and return each vector that way, right? — tmwcheese, Jul 28 '14 at 16:58

Create a vector of strings in one file and use it in another file

1 Answers1