cannot access argv value in functions that are initialized in constructor

Question

Unable to access argv value in parseCmdline function in myarm.cpp which is initialized in the constructor. Don't know how to pass/initialize the value from main(int argc, char *argv[ ]) in constructor?

main.cpp

#include "myarm.h"    
int main(int argc, char *argv[]){
    cout<<"argv is:"<<argv[2]<<endl;
    MyArm arm;

myarm.cpp

#include "myarm.h"

MyArm::MyArm(){
    nj = 0;
    done = false;
    times = 0;
    count = 50;
    which_joint = 0;
    cout<<"argv is:"<<argv[2]<<endl;
    parseCmdline();
}

int MyArm::parseCmdline() {
    params.fromCommand(argc, argv);
    if (!params.check("robot")){
        cout<<"Please specify name of the robot"<<endl;
        cout<<"--robot name (e.g. TechNit)"<<endl;
        return 1;
    }

    else if(!params.check("element")){
        cout<<"Please specify name of the element"<<endl;
        cout<<"--element name (e.g. left_arm)"<<endl;
        return 1;
    }
}

Typically you'd want to handle the params outside of the object. — erip, Nov 29 '15 at 19:47
Your code is much too complicated. You are trying to pass a command-line argument to a constructor. Do you know how to pass a command-line argument to a function? Do you know how to pass an argument to a constructor? — Beta, Nov 29 '15 at 19:49

score 0 · Answer 1 · answered Nov 29 '15 at 19:48

Passing the parameters from main to other functions is easy, just declare the other functions like main:

void my_method(int argument_count, char * * arg_list);

int main(int argument_count, char * * arg_list)
{
  my_method(argument_count, arg_list);
  return EXIT_SUCCESS;
}

void my_method(int argument_count, char * * arg_list)
{
  std::cout << "Argument Count: " << argument_count << "\n";
  for (int i = 0; i < argument_count; ++i)
  {
    std::cout << "Argument [" << i << "]: " << arg_list[i] << "\n";
  }
}

i got this but the problem is that i am unable to use argv in the line params.fromCommand(argc, argv); which belongs to a header file. — Nabeeha Deedar, Nov 29 '15 at 20:11

score 0 · Answer 2 · edited May 23 '17 at 12:07

0

Add parameters to the constructor:

MyArm::MyArm(int argc, char *argv[])

then instantiate as

MyArm arm(argc, argv);

Edit

but it turns out these parameters need to be used by

int MyArm::parseCmdline()

so parseCmdline also needs to be redefined

int MyArm::parseCmdline(int argc, char *argv[])

and called with

parseCmdline(argc, argv);

See the pattern? If not, I recommend giving the text book a deeper read or getting a better text book.

edited May 23 '17 at 12:07

Community

1
1

answered Nov 29 '15 at 19:49

user4581301

33,082
7
33
54

Got it, but now getting error: ‘argv’ was not declared in this scope which is in myarm.cpp in the above code. How to pass value of argv to this function? params.fromCommand(argc, argv); – Nabeeha Deedar Nov 29 '15 at 20:01
1

@Nabeeha Deedar: You can't use arc or argv in your constructor MyArm::MyArm() because you didn't pass them to it. Pass them during instantiation and if you need them for other member functions, make them members – Bob__ Nov 29 '15 at 20:48

cannot access argv value in functions that are initialized in constructor

2 Answers2

Edit