Blank string input first time through loop? (c++) [duplicate] - c++

Question

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Why does std::getline() skip input after a formatted extraction?
(5 answers)
Closed 6 years ago.
I'm trying to get user input of names to store in a vector.
Every time I run through the for loop, it always takes blank input in the temp string variable the first time through the loop.
What I get when I run this program is something like:
,
Dylan, Bob
Brown, Mark
Rogers, Mr
Thanks for any help
Sorry first post =P
Heres the code:
#include <iostream>
#include <iomanip>
#include <string>
#include <vector>
#include <fstream>
using namespace std;
void getNames(vector<string> &n, int&);
void displayNames(vector<string> &n, int&);
void saveNames(vector<string> &n, int&);
void readNames(vector<string> &n, int&);
void sortNames(vector<string> &n, int&);
int main(){
vector<string> names;
int b = 0;
int choice;
while(choice != 5){
cout << "1 - Enter a Character" << endl;
cout << "2 - Display List of Characters" << endl;
cout << "3 - Save List of Characters to File" << endl;
cout << "4 - Read List of Characters from File" << endl;
cout << "5 - Exit the program" << endl << endl;
cin >> choice;
switch(choice){
case 1: getNames(names, b); break;
case 2: displayNames(names, b); break;
case 3: saveNames(names, b); break;
case 4: readNames(names, b); break;
}
}
return 0;
}
void getNames(vector<string> &n, int &b){
string temp;
cout << "Enter Names. Press \'quit\' to stop." << endl;
for(b; temp != "quit"; b++){
getline(cin, temp);
if(temp == "quit"){
break;
}else{
int space = temp.find(' ', 0);
string inPut = temp.substr((space+1), temp.length());
inPut += ", ";
inPut += temp.substr(0, space);
n.push_back(inPut);
}
}
}
void displayNames(vector<string> &n, int &b){
for(int c=0; c < b; c++){
cout << n[c] << endl;
}
}
void saveNames(vector<string> &n, int &b){
ofstream outFile;
outFile.open("names.txt", ios::app);
if(!outFile.fail()){
for(int i=0; i < b; i++){
outFile << n[i] << endl;
}
cout << "Names written to File" << endl;
}else{
cout << "ERROR: File could not be opened" << endl;
}
outFile.close();
}
void readNames(vector<string> &n, int&){
string line;
ifstream inFile("names.txt");
if(inFile.is_open()){
while(getline(inFile, line)){
cout << line << endl;
}
inFile.close();
}else{
cout << "Cannot open File" << endl;
}
}
void sortNames(vector<string> &n, int&){
//for(int i=0; i < b; i++){}
}

Answer 1

By fixing your curly braces your getNames() function works for me as expected. Maybe this is an oversight from posting your code, but you are missing a curly brace to end your for loop and function call for GetNames(). Compiling and using this code produces the expected output:
void getNames(vector<string> &n, int &b){
string temp;
cout << "Enter Names. Press \'quit\' to stop." << endl;
for(b; temp != "quit"; b++){
getline(cin, temp);
if(temp == "quit"){
break;
}else{
int space = temp.find(' ', 0);
string inPut = temp.substr((space+1), temp.length());
inPut += ", ";
inPut += temp.substr(0, space);
cout << inPut << endl; //Testing string transformation before insertion.
n.push_back(inPut);
}
}
}
Passing the names: "Bob Dylan", "Jerry McQuire", and "Some Guy" resulted in the output
Dylan, Bob
McQuire, Jerry
Guy, Some
It is possible that there is an error somewhere else in the code if your first element in the Vector is always blank. The error is possibly in the saveNames() or readNames() functions. But the strings are input and transformed correctly here. It's beneficial to post all the code relevant to your question ahead of time.
Please include this at the top of getNames():
cin.clear();
cin.ignore(10000, '\n');
This will clear the cin buffer to a new line so the initial choice from main() doesn't get put in to the vector unexpectedly.

Answer 2

Why are you using a for loop? is better to use a while loop like so:
void getNames(vector<string> &n, int &b)
{
string temp;
cout << "Enter Names. Press \'quit\' to stop." << endl;
getline(cin, temp);
while(temp != "quit")
{
int space = temp.find(' ', 0);
string inPut = temp.substr((space+1), temp.length());
inPut += ", ";
inPut += temp.substr(0, space);
n.push_back(inPut);
getline(cin, temp);
}
...//the rest of your code...
}
I didn't answer the question, sorry... the first input is the termination character of your last cin... std::getline (string)