I know this post has been made before on stack overflow, and I have combined various tutorials; but why does this code cause an error on execution - it does compile.
void leaderBoard::loadFromFile(void)
{
string line;
ifstream leaderBoardFile ("leaderboard.data");
vector<string> playerInfoVector;
if (leaderBoardFile.is_open())
{
while ( leaderBoardFile.good() )
{
playerInfoVector.clear();
getline (leaderBoardFile,line);
std::string input = line;
std::istringstream ss(input);
std::string token;
//cout << line << endl;
while(getline(ss, token, ',')) {
//for current line;
playerInfoVector.push_back(token);
}
string firstName = playerInfoVector.at(0);
string stringAge = playerInfoVector.at(1);
string stringScore = playerInfoVector.at(2);
//int age;
//stringstream(stringAge) >> age;
//int score;
//stringstream(stringScore) >> score;
//addScore(firstName,age,score);
////stringstream(stringAge) >> age;
////Add text to vector (push back)
playerInfoVector.clear();
}
leaderBoardFile.close();
}
else cout << "Unable to open file";
}
Yes loads of times
while ( leaderBoardFile.good() )
{
playerInfoVector.clear();
getline (leaderBoardFile,line);
should be
while ( getline (leaderBoardFile,line) )
{
playerInfoVector.clear();
It is incredible how many times this error is repeated. You actually got it right in your second while loop, so why wrong in the first one?
Unfortunately some tutorials also get this wrong.
It would also be sensible to add a check that you really do have three items in your vector. Something like this
if (playerInfoVector.size() < 3)
{
cerr << "Not enough items in player info vector\n";
exit(1);
}
string firstName = playerInfoVector.at(0);
string stringAge = playerInfoVector.at(1);
string stringScore = playerInfoVector.at(2);
Related
I am trying to read lines of a file (cityName, hiTemp, loTemp) into a struct array. I was able to use >> to read the first several lines until I hit a city with a space in it's name.
I then tried using getline() to read the lines, but then my while loop stopped working.
I have no clue why this would happen.
int LoadData()
{
int count = 0;
string path;
cout << "Specify the input file path: ";
ifstream inFile;
cin >> path;
inFile.open(path.c_str());
if (!inFile.is_open())
{
cout << "Error - could not open file: " << path;
return (-1);
}
else
{
while (!inFile.eof())
{
cities[count].city = "";
getline(inFile, cities[count].city);
if (cities[count].city.length() == 0)
{
break;
}
char comma;
inFile >> (cities[count].high) >> comma >> cities[count].low;
cout << cities[count].city << " " << cities[count].high << " " << cities[count].low << endl;
count++;
}
inFile.close();
inFile.clear(std::ios_base::goodbit);
return count;
}
}
while (!inFile.eof())
For getting every line in the file, you should use:
while(getline(inFile, cities[count].city)) {
// ...
This works and is recommended over using the .eof() method.
You can also use this in your if-statement:
if (!getline(inFile, str))
break;
As an aside, you can read this site:
Why is “while ( !feof (file) )” always wrong? - StackOverflow post
It gives insight into why using the .eof() is not the preferred method to use in a while loop to check whether the end-of-file has been reached.
Use getline as loop condition. You can also replace the second read with a getline too and use a stringstream to parse it.
#include <sstream>
// ...
while(getline(inFile, cities[count].city)) {
if (cities[count].city.empty()) break;
// read next line with high and low values
string str;
if (!getline(inFile, str)) break; // error in file format
stringstream ss(str);
char comma;
ss >> cities[count].high >> comma >> cities[count].low; // parse it
}
I have a text file that has information format like this:
id last,first string
for example:
0 Snow,John nothing
1 Norris,Chuck everything
How do i get last name and first name stored separately?
To get information from file, I did:
#include <fstream>
int id;
string str;
string last;
string first;
int main()
{
ifstream myfile(ex.txt);
myfile >> id;
while (myfile)
{
for (int i = 0; i < 4; i++) // this is the amount of times i'll get information from 1 line
{
id = id; // its actually some_structure.id = id, omit
getline(myfile, last, ','); // i think i need to use another function as getline get the whole line
cout << id;
cout << last; // print out the whole line!
}
}
}
ifstream myfile;
string line;
while (getline(myfile, line))
{
istringstream ss(line);
int id;
ss >> id;
string fullname;
ss >> fullname;
string firstname, lastname;
{
istringstream ss2(fullname);
getline(ss2, lastname, ',');
getline(ss2, firstname);
}
}
if (std::ifstream input(filename))
{
int id;
string lastname, firstname, other_string;
while (input >> id && getline(input, lastname, ',') &&
input >> firstname >> other_string)
... do whatever you like...
if (!input.eof())
std::cerr << "error while parsing input\n";
}
else
std::cerr << "error while opening " << filename << '\n';
The code above has more error checking than the other answers I've seen, but admittedly - because it doesn't read text a line at a time then parse out the fields, it would happily accept e.g.:
10 Chuck,
Norris whatever
Would recomend something like this:
string name;
myfile >> id >> name >> str;
first = name.substr(0, name.find(","));
last = name.substr(name.find(",") + 1);
Note that your EOF checking is incorrect.
// The complete code that will do the job
// Please remove uncomment all code
#include <iostream>
#include <fstream>
#include <string>
using namespace std;
int main () {
string line;
ifstream myfile ("ex.txt");
if (myfile.is_open())
{
while ( getline (myfile,line) )
{
cout << line << '\n';
string last = line.substr(line.find(" ") + 1, line.find(",") - 2);
string first = line.substr(line.find(",") + 1, line.find(",") + line.find(" ") - 1);
}
myfile.close();
}
else {
cout << "Unable to open file";
}
return 0;
}
I have a text file that displays the following:
John Smith 21 UK
David Jones 28 FRANCE
Peter Coleman 18 UK
and I am trying to strip each individual element into a vector array. I have tried using the getline function with a tab delimiter but it stores every element. For example:
getline (f, line, '\t');
records.push_back(line);
How can I seperate it line by line? The idea is to perform a search and output the corresponding line. A search for Jones will print out the second line for example.
This is what I have so far but as you can see, it's not giving me the desired outcome:
string sString;
string line;
string tempLine;
string str;
vector<string> records;
cout << "Enter search value: " << endl;
cin >> sString;
cout << "\nSEARCHING\n\n";
ifstream f("dataFile.txt");
while (f)
{
while(getline (f, tempLine))
{
getline (f, line, '\t');
records.push_back(line);
}
for(int i=0; i < records.size(); i++)
{
if(sString == records[i]) {
cout << "RECORD FOUND" << endl;
for(int j=0; j < records.size(); j++)
{
cout << j;
cout << records[j] << "\t";
}
}
}
}
f.close();
The first getline extracts a complete line from the input.
The second extracts one field from the next line. If you want
to recover the lines broken down into fields, you should do:
std::vector<std::vector<std::string>> records;
std::string line;
while ( std::getline( f, line ) ) {
records.push_back( std::vector<std::string>() );
std::istringsream fieldParser( line );
std::string field;
while ( std::getline( fieldParser, field ) ) {
records.back().push_back( field );
}
}
This will result in a vector of records, where each record is
a vector of fields. More often, you would want to use a struct
for the record, and do a bit more parsing on the line, e.g.:
struct Field
{
std::string firstName;
std::string lastName;
int age;
std::string country;
};
std::vector<Field> records;
std::string line;
while ( std::getline( f, line ) ) {
std::istringsream fieldParser( line );
Field field;
fieldParser >> field.firstName >> field.lastName >> field.age >> field.country >> std::skipws;
if ( !fieldParser || fieldParser.get() != EOF ) {
// Error occurred...
} else {
records.push_back( field );
}
}
(Something this simple will only work if none of the fields may
contain white space. But it's simple to extend.)
You are doing getline into tempLine which eats a whole line, then you are doing a different getline in the loop as well. That's a big part of why it doesn't work--you are simply throwing away tempLine which contains a lot of your data.
How do I read in lines from a file and assign specific segments of that line to the information in structs? And how can I stop at a blank line, then continue again until end of file is reached?
Background: I am building a program that will take an input file, read in information, and use double hashing for that information to be put in the correct index of the hashtable.
Suppose I have the struct:
struct Data
{
string city;
string state;
string zipCode;
};
But the lines in the file are in the following format:
20
85086,Phoenix,Arizona
56065,Minneapolis,Minnesota
85281
56065
I cannot seem to figure this out. I am having a really hard time reading in the file. The first line is basically the size of the hash table to be constructed. The next blank line should be ignored. Then the next two lines are information that should go into the struct and be hashed into the hash table. Then another blank line should be ignored. And finally, the last two lines are input that need to be matched to see if they exist in the hash table or not. So in this case, 85281 is not found. While 56065 is found.
This is what I have and it doesn't seem to be doing what I want it to do:
int main(int argc, char *argv[])
{
string str;
//first line of file is size of hashtable
getline(cin, str);
stringstream ss(str);
int hashSize;
ss >> hashSize;
//construct hash table
Location *hashTable = new Location[hashSize];
//skip next line
getline(cin, str);
string blank = " ";
while(getline(cin, str))
{
{
//next lines are data
Location locate;
string line;
getline(cin, line);
istringstream is(line);
getline(is, locate.zipCode, ',');
getline(is, locate.city, ',');
getline(is, locate.state, ',');
insertElementIntoHash(hashTable, locate, hashSize);
}
}
dispHashTable(hashTable, hashSize);
//read third set of lines that check if the zipCodes are in the hashtable or not
while(getline(cin, str))
{
//stop reading at a blank line or in this case, end of file
stringstream is(str);
string searchZipCode;
is >> searchZipCode;
searchElementInHash(hashTable, hashSize, searchZipCode);
}
//delete hash table after use
delete []hashTable;
return 0;
}
You might read the input this way:
#include <iostream>
#include <sstream>
#include <vector>
struct Location
{
std::string city;
std::string state;
std::string zipCode;
};
int main(int argc, char *argv[]) {
std::istringstream input(
"2\n"
"\n"
"85086,Phoenix,Arizona\n"
"56065,Minneapolis,Minnesota\n"
"\n"
"85281\n"
"56065\n"
);
// Make the size unsigned, to avoid signed/unsigned compare warnings.
unsigned hashSize;
std::string line;
getline(input, line);
std::istringstream hash_line(line);
// Ignore white space.
if( ! (hash_line >> hashSize >> std::ws && hash_line.eof())) {
std::cerr << "Error: Invalid file format [1].\n" << line << '\n';
return -1;
}
else {
getline(input, line);
std::istringstream first_blank_line(line);
// Ignore white space.
first_blank_line >> std::ws;
if( ! first_blank_line.eof()) {
// Missing blank line.
std::cerr << "Error: Invalid file format [2].\n" << line << '\n';
return -2;
}
else {
// Have a local variable (No need to allocate it)
// (Is it a hash table !???)
std::vector<Location> hashTable;
hashTable.reserve(hashSize);
while(hashTable.size() < hashSize && getline(input, line)) {
std::istringstream data_line(line);
Location locate;
getline(data_line, locate.zipCode, ',');
getline(data_line, locate.city, ',');
getline(data_line, locate.state); // Note: No comma here.
if(data_line && data_line.eof()) {
// Note: The fields may have leading and/or trailing white space.
std::cout
<< "Insert the location into the hash table.\n"
<< locate.zipCode << '\n'
<< locate.city << '\n'
<< locate.state << '\n';
hashTable.push_back(locate);
}
else {
std::cerr << "Error: Invalid file format [3].\n" << line << '\n';
return -3;
}
}
if(hashTable.size() != hashSize) {
std::cerr << "Error: Invalid file format [4].\n";
return -4;
}
else {
getline(input, line);
std::istringstream second_blank_line(line);
// Ignore white space.
second_blank_line >> std::ws;
if( ! second_blank_line.eof()) {
// Missing blank line.
std::cerr << "Error: Invalid file format [5].\n";
return -5;
}
else {
std::string searchZipCode;
while(input >> searchZipCode) {
// Search element in the hash table
}
}
}
}
}
return 0;
}
Following modification should work:
//skip next line
getline(cin, str);
string blank = " ";
string line;
while(getline(cin, line) && (line != ""))
{
{
//next lines are data
Location locate;
istringstream is(line);
getline(is, locate.zipCode, ',');
getline(is, locate.city, ',');
getline(is, locate.state, ',');
insertElementIntoHash(hashTable, locate, hashSize);
}
}
I have a txt file that contains name, id number, mobilenumber, and location in comma separated line.
example
Robby, 7890,7788992356, 123 westminister
tom, 8820, 77882345, 124 kingston road
My task is to retrieve
Look up all of an employee's information by name.
Look up all of an employee's information by ID.
Add the information of an employee.
Update the information of an employee.
SO far I have read the file and stored the information in a vector. Code is shown below.
For tasks
1)Look up all of an employee's information by name. I will iterate in the vector and prints information containing the name . I will be able to do that
2) simialry in text file I will look for id and prints information about that.
BUT I am clueless about point 3 & 4.
I am posting my code below
void filter_text( vector<string> *words, string name)
{
vector<string>::iterator startIt = words->begin();
vector<string>::iterator endIt = words->end();
if( !name.size() )
std::cout << " no word to found for empty string ";
while( startIt != endIt)
{
string::size_type pos = 0;
while( (pos = (*startIt).find_first_of(name, pos) ) != string::npos)
std:cout <<" the name is " << *startIt<< end;
startIt++;
}
}
int main()
{
// to read a text file
std::string file_name;
std::cout << " please enter the file name to parse" ;
std::cin >> file_name;
//open text file for input
ifstream infile(file_name.c_str(), ios::in) ;
if(! infile)
{
std::cerr <<" failed to open file\n";
exit(-1);
}
vector<string> *lines_of_text = new vector<string>;
string textline;
while(getline(infile, textline, '\n'))
{
std::cout <<" line text:" << textline <<std::endl;
lines_of_text->push_back(textline);
}
filter_text( lines_of_text, "tony");
return 0;
}
#include <string>
#include <iostream>
#include <vector>
#include <stdexcept>
#include <fstream>
struct bird {
std::string name;
int weight;
int height;
};
bird& find_bird_by_name(std::vector<bird>& birds, const std::string& name) {
for(unsigned int i=0; i<birds.size(); ++i) {
if (birds[i].name == name)
return birds[i];
}
throw std::runtime_error("BIRD NOT FOUND");
}
bird& find_bird_by_weight(std::vector<bird>& birds, int weight) {
for(unsigned int i=0; i<birds.size(); ++i) {
if (birds[i].weight< weight)
return birds[i];
}
throw std::runtime_error("BIRD NOT FOUND");
}
int main() {
std::ifstream infile("birds.txt");
char comma;
bird newbird;
std::vector<bird> birds;
//load in all the birds
while (infile >> newbird.name >> comma >> newbird.weight >> comma >> newbird.height)
birds.push_back(newbird);
//find bird by name
bird& namebird = find_bird_by_name(birds, "Crow");
std::cout << "found " << namebird.name << '\n';
//find bird by weight
bird& weightbird = find_bird_by_weight(birds, 10);
std::cout << "found " << weightbird.name << '\n';
//add a bird
std::cout << "Bird name: ";
std::cin >> newbird.name;
std::cout << "Bird weight: ";
std::cin >> newbird.weight;
std::cout << "Bird height: ";
std::cin >> newbird.height;
birds.push_back(newbird);
//update a bird
bird& editbird = find_bird_by_name(birds, "Raven");
editbird.weight = 1000000;
return 0;
}
Obviously not employees, because that would make your homework too easy.
So, first off, I don't think you should store the information in a vector of strings. This kind of task totally calls for the use of a
struct employee {
int id;
std::string name;
std::string address;
//... more info
};
And storing instances of employees in an
std::vector<employee>
You see, using your strategy of storing the lines, searching for "westminster" would net me Robbie, as his line of text does include this substring, but his name isn't westminster at all. Storing the data in a vector of employee structs would eliminate this problem, and it'd make the whole thing a lot more, well, structured.
Of course you'd need to actually parse the file to get the info into the vector. I'd suggest using a strategy like:
while(getline(infile, textline, '\n')) {
std::stringstream l(textline);
getline(l,oneEmp.name, ','); //extract his name using getline
l >> oneEmp.id; //extract his id
//extract other fields from the stringstream as neccessary
employees.push_back(oneEmp);
}
As for adding information: when the user enters the data, just store it in your employees vector; and when you should need to update the file, you may simply overwrite the original data file with a new one by opening it for writing & dumping the data there (this is obviously a rather wasteful strategy, but it's fine for a school assignment (I suppose it's school assignment)).
Start by splitting the CSV line into separate fields and then populate a struct with this data
eg:
struct Employee
{
std::string name;
std::string id_number;
std::string mobilenumber;
std::string location;
};
std::vector<Employee> employees; // Note you dont need a pointer
Look at string methods find_first_of, substr and friends.