Loop Issues with objects in C++ - c++

Question

I have to create a simple code that is supposed to create a .txt file as an output, containing a list fo notations with this format. (time ; topic ; comment)
the code has to run a loop using a struct function showed below:
struct annotation_t {
string topic;
string comment;
time_t stamp;
};
so the user can input the notations as many times he wants till he decides to go out. This is what I did so far.
#include <iostream>
#include <string>
#include <ctime>
#include <fstream>
#include <cstdlib>
#include <vector>
using namespace std;
struct annotation_t {
string topic;
string comment;
time_t stamp;
};
int main()
{
int q = 0;
std::vector<annotation_t> obj;
do
{
annotation_t temp = {};
cout<< "input your topic: ";
cin >> temp.topic ;
cout<< "input yourfeedback: ";
cin >> temp.comment ;
cout<< "input your time stamp: ";
cin >> temp.stamp ;
cout<< "exit?";
cin >> q;
obj.push_back(temp);
} while (q != 0);
ofstream myfile("annotation.txt");
char time[1000];
for(int i = 0;i<50;i++)
{
struct annotation_t obj[i];
myfile<<obj[i].stamp <<" "; // write in file
myfile<<obj[i].topic <<" ";// write in file
myfile<<obj[i].comment; // write in file
myfile<<"\n";
}
cout<<"\nFile Created with Data with name annotation.txt \n";
myfile.close();
system("Pause");
}
I have a problem when it come to exit. if I input any value( even 0) I get a segmentation fault so i am not able to quit the loop and save my file in the txt, or re run it if I want to input more.. Let me know your thoughts.thanks

Answer 1

int i=0;
struct annotation_t obj[i];
You're making an array of annotation_t objects of 0 size
cin >> obj[i].topic ;
Then attempting to access the first element.
Consider using std::vector instead, which will allow you to dynamically change the size of your container to allow the user to input as many as they'd like:
// Empty container
std::vector<annotation_t> obj;
do
{
// Create temporary
annotation_t temp = {};
// Accept input:
cin >> temp.topic;
...
// Add to container:
obj.push_back(temp);
}
In your beneath for loop, you are doing the same thing as above
for(int i = 0;i<50;i++)
{
struct annotation_t obj[i];
Plus, you are creating a new container. You probably intend to use the container from above, which will change your loop into:
// Store the contents of the now populated obj from above
for (auto& a : obj)
{
myfile << a.stamp << " ";
myfile << a.topic << " ";
myfile << a.comment << std::endl;
}

Answer 2

You have problem with declaration 'obj' object.
This is wrong :
struct annotation_t obj[i];
Try this instead :
#include <iostream>
#include <string>
#include <ctime>
#include <fstream>
#include <cstdlib>
using namespace std;
struct annotation_t {
string topic;
string comment;
time_t stamp;
};
int main()
{
int q = 0;
struct annotation_t obj[1000]; //msf
int i=0; //msf
do
{
cout<< "input your topic";
cin >> obj[i].topic ;
cout<< "input yourfeedback";
cin >> obj[i].comment ;
cout<< "input your time stamp";
cin >> obj[i].stamp ;
cout<< "exit?";
cin >> q ;
i++; //msf
} while (q != 0);
ofstream myfile("annotation.txt");
int count=i; //msf
for(i = 0;i<count;i++) //msf
{
myfile<<obj[i].stamp <<" "; // write in file
myfile<<obj[i].topic <<" ";// write in file
myfile<<obj[i].comment; // write in file
myfile<<"\n";
}
cout<<"\nFile Created with Data with name annotation.txt \n";
myfile.close();
system("Pause");
}
I changed your code in many positions that I commented with '//msf'.
I don't have C++ compiler in hand then I hope it will be compiled without errors.