error while trying to get the int from a string

Question

I want to get the int from the string, without using the int type directly to get advantages from getline() but somehow I get an error if the input is not an actual int.

#include <iostream>
#include <string>

using namespace std;

int main (int argc, char** argv)
{
    string word = {0};

    cout << "Enter the number 5 : ";

    getline(cin, word);

    int i_word = stoi(word);

    cout << "Your answer : " << i_word << endl;

    return 0;
}

When the user input is 5 (or any other int) the output is :

Enter the number 5 : 5
Your answer : 5

When the user input is either ENTER or any other letter, word, etc... :

Enter the number 5 : e
terminate called after throwing an instance of 'std::invalid_argument'
  what():  stoi
Abandon (core dumped)

4

Read up on exception handling – RvdK Jan 25 '16 at 10:08

RvdK · Accepted Answer · 2016-01-25T10:54:49.333

4

It's called exception handling:

try
{
    int i_word = stoi(word);

    cout << "Your answer : " << i_word << endl;
} 
catch (const std::invalid_argument& e)
{
    cout << "Invalid answer : " << word << endl;
}
catch (const std::out_of_range& e)
{
    cout << "Invalid answer : " << word << endl;
}

edited Jan 25 '16 at 10:54

answered Jan 25 '16 at 10:10

RvdK

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Neat, exactly what I needed. I didn't know there was exception handling mecanism in c++, I'm trying to learn on my own. Thanks a lot for your quick&clear answer. – Amin NAIRI Jan 25 '16 at 10:16
@Gradiuss Perhaps learning from a book would be a better option. – eerorika Jan 25 '16 at 10:25
That's what I was thinking, but for now I'm kind of testing what suits me best between C and C++ but I find C++ handy and easy to learn. But thanks for the advice @user2079303 – Amin NAIRI Jan 25 '16 at 10:30
I would prefer C++: here is great tutorial http://www.cplusplus.com/doc/tutorial/ – RvdK Jan 25 '16 at 10:32
It also needs `catch(std::out_of_range& e)` – Barmak Shemirani Jan 25 '16 at 10:32
Is there something like else catch ? – Amin NAIRI Jan 25 '16 at 10:39
@Gradiuss what do you mean? – RvdK Jan 25 '16 at 10:43
You said it also needs to catch if out of range right so I just to add another catch() or is there something like if () else if () else () ? – Amin NAIRI Jan 25 '16 at 10:52
It's clearly explained in the tutorial I posted: http://www.cplusplus.com/doc/tutorial/exceptions/ (updated answer) – RvdK Jan 25 '16 at 10:55

error while trying to get the int from a string

1 Answers1