Passing a user input string in a different function in C++

Question

I am very new to C++ and I am having a difficult time passing by reference/value?

I am attempting to pass the user input string from the get_sentence function into the replace_message function and replace the characters with underscores, but I it will not do that?

I am sorry if this is not specific enough, but I could really use some help.

int main() {
    string hidden, public_string;
    get_sentence();
    replace_message(hidden);
    return 0;
}

string get_sentence() {
    string hidden;
    cout << "Enter a message: ";
    getline (cin, hidden);
    return hidden;
}         

string replace_message(string &hidden) {
    string public_string;
     hidden = public_string;
    for(int i=0; i< public_string.length(); i++) {
      if(public_string[i] != ' ')
         public_string[i] = '_';
    }
    cout << "The message is" << public_string << endl;
    return public_string;
}

Is C++ your first OO language? If yes, I'd recommend learning something easier to grasp the basics of procedural programming and OO paradigm. I'd go for C#, but Java would work as well. With C++, you can run in all sorts of seemingly weird problems. — Oskar Hýbl
– Oskar Hýbl, Commented Feb 18, 2016 at 7:55
At my school they start us with C++ so everything will seem easier afterward. — Haley Coutts
– Haley Coutts, Commented Feb 18, 2016 at 8:02
Well... it certainly will, there is no arguing with that. Good luck then! — Oskar Hýbl
– Oskar Hýbl, Commented Feb 18, 2016 at 8:06

Tim Biegeleisen · Accepted Answer · 2016-02-18 07:48:27Z

5

Modify your main() method to use the result which is returned from the get_sentence() function:

int main() {
    string hidden, public_string;

    hidden = get_sentence();      // store user message here
    replace_message(hidden);      // and pass it here

    return 0;
}

You should also modify your replace_message() function to use the input you pass to it:

string replace_message(string &hidden) {
    string public_string = hidden;

    for (int i=0; i< public_string.length(); i++)
    {
        if (public_string[i] != ' ')
            public_string[i] = '_';
    }

    cout << "The message is" << public_string << endl;

    return public_string;
}

answered Feb 18, 2016 at 7:48

Tim Biegeleisen

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2 Comments

RHertel Over a year ago

What is the use of returning public_string by replace_message if the returned string isn't stored in main? It would seem to make more sense if the function was void.

Tim Biegeleisen Over a year ago

@RHertel Good point. He could consider making the function void, or if he actually intends to use the returned string later in his software project, he could leave it as is.

Anirudh · Accepted Answer · 2016-02-18 07:50:19Z

4

int main(){
string hidden;

hidden = get_sentence();

replace_message(hidden);

return 0;
}

You function is returning a value but you have to store that in a variable. Your replace_message function is also buggy because you are assigning and unintialized string public_string to your original message in the variable hidden. Do it as follows

void replace_message(string &hidden){

for(int i=0; i< hidden.length(); i++)
{
  if(hidden[i] != ' ')
     hidden[i] = '_';
}

cout << "The message is" << hidden << endl;
}

answered Feb 18, 2016 at 7:50

Anirudh

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Comments

RHertel · Accepted Answer · 2016-02-18 09:45:12Z

0

You could also avoid the loop and use std::regex_replace instead:

#include <iostream>
#include <regex>
#include <string>
using namespace std;
string get_sentence() {
    string hidden;
    cout << "Enter a message: ";
    getline (cin, hidden);
    return hidden;
}         

string replace_message(string &hidden) {
  regex non_blank("\\S"); // selects everything but whitespace characters
  string public_string = regex_replace(hidden, non_blank, "_");
  return public_string;
}

int main() {
    string hidden, public_string;
    hidden = get_sentence();
    public_string = replace_message(hidden);
    cout << "The message is: " << public_string << endl;
    return 0;
}

edited Feb 18, 2016 at 9:45

answered Feb 18, 2016 at 9:28

RHertel

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