I have three string file that will be stored into dynamic array, but I just try one of three file to test if this succed, so I'll do the same way to handle the three file i have.
the goal i'll shown the string that I get from the file to a ListView
this my code.
void __fastcall TFrmNewPeta::showDefaultRute() {
std::string lineDataAwal;
std::ifstream ifs_Awal;
int tempIndexAwal = 0;
ifs_Awal.open("DefaultDataAwal");
/*counting the line*/
while(std::getline(ifs_Awal,lineDataAwal)){++tempIndexAwal;}
/*use dynamic array to stored string*/
std::string *s = new std::string[tempIndexAwal];
for(int dx=0;dx<tempIndexAwal;dx++)
{
while(std::getline(ifs_Awal,lineDataAwal))
s[dx] = lineDataAwal[dx++];
}
for(int dex =0;dex<tempIndexAwal;++dex)
{
ItemDefult = ListView1->Items->Add();
ItemDefult->Caption = String(IntToStr(dex + 1));
ItemDefult->SubItems->Add(s[dex].c_str());
}
ifs_Awal.close();
delete []s;
s = NULL;
}
there's no errors during compile, but the result ListView just showing the number with this code ItemDefult->Caption = String(IntToStr(dex + 1));
can anyone show me how the best way for i do.
You are reading the file, leaving it open, and expecting to read it again. That won't work because the cursor in the file is at the end of the file (so your second while loop does nothing).
A much better approach would be:
std::vector<std::string> lines;
std::string line;
std::ifstream fin("Youfilename");
while (std::getline(fin, line))
{
lines.push_back(line);
}
fin.close();
// add data to your list view
its easier if you use std::vector for dynamic arrays and don't forget to first include the file header with #include<vector>
void __fastcall TFrmNewPeta::showDefaultRute() {
std::string lineDataAwal;
std::ifstream ifs_Awal;
std::vector<std::string> vec;
ifs_Awal.open("DefaultDataAwal");
/*get the string of lineDataAwal */
while(std::getline(ifs_Awal,lineDataAwal))
{ vec.push_back(lineDataAwal);}
for(int dex =0;dex<vec.size();++dex)
{
ItemDefult = ListView1->Items->Add();
ItemDefult->Caption = String(IntToStr(dex + 1));
ItemDefult->SubItems->Add(vec.at(dex).c_str());
}
ifs_Awal.close();
}
Hope this helps
Related
My code should read in from ".csv" file given in the arguments, to a 2D vector table. Everytime I tried to run it it said "Segmentation fault (core dumped). I even tried to get it fiexed with gdb (g++ debugger) in console. The closest I've got to the promblem is this message:
Program received signal SIGSEGV, Segmentation fault.
__memmove_sse2_unaligned_erms () at ../sysdeps/x86_64/multiarch/memmove-vec-unaligned-erms.S:314
314 ../sysdeps/x86_64/multiarch/memmove-vec-unaligned-erms.S: No such
file or directory.
I don't know what should I do to fix it.
void Table::read_file(std::string f_str) {
std::fstream file;
std::string line;
file.open(f_str, std::ios::in);
if (!file) { incorrect_input(); }
else {
while (std::getline(file, line)) // first while to resize our 2d vector table
{
std::istringstream iss(line);
std::string result;
int cols = 1;
while (std::getline(iss, result, sep))
{
cols++;
}
if (getColumn() < cols) { setColumn(cols); }
setRow(getRow() + 1);
}
file.clear();
file.seekg(0, std::ios_base::beg);
int i = 0;
int j = 0;
while (std::getline(file, line)) // second while to get the records segmented in to our 2d vector table 'cells'
{
std::istringstream iss(line);
std::string result;
while (std::getline(iss, result, sep))
{
cellcontainer[i][j] = result;
j += 1;
}
i += 1;
}
}
file.close();
}
udpate:
So the cellcontainer is a 2D vector table/matrix. It's constructed by a header file, main calls for it at the start of the code, after the ".csv" file is given through arguments. It contains the "cells" of the 2D vector table. And it looks like this in header:
class Table {
private:
std::vector<std::vector<std::string>> cellcontainer;
int row;
int column;
char sep = ';';
public:
Table() : row(1), column(1) {
cellcontainer.push_back(std::vector<std::string>());
cellcontainer[0].push_back("-");
}
update_2:
I rewrote this line cellcontainer[i][j] = result;
To this cellcontainer.at(i).at(j) = result;
And it says std::out_of_range
Thankfully for everyone but specially for Raymond Chen.
solution was: At the first while() of my code I only kept the columns and rows of the class variables updated and did not even changed the size of my container of the 2D vectors (cellcontainer).
Now it looks like this:
while (std::getline(iss, result, sep))
{
addColumn(1); // <-- addColumn() function arg is an int and it adds to our cellcontainer with resizing.
cols++;
}
if (getColumn() < cols) { setColumn(cols); }
setRow(getRow() + 1);
addRow(1); // <-- addRow() function arg is an int and it adds to our cellcontainer with resizing
I'm having slight trouble creating a 2D Vector of String that's created by reading values from a text file. I initially thought I needed to use an array. however I've come to realise that a vector would be much more suited to what I'm trying to achieve.
Here's my code so far:
I've initialised the vector globally, but haven't given it the number of rows or columns because I want that to be determined when we read the file:
vector<vector<string>> data;
Test data in the file called "test" currently looks like this:
test1 test2 test3
blue1 blue2 blue3
frog1 frog2 frog3
I then have a function that opens the file and attempts to copy over the strings from text.txt to the vector.
void createVector()
{
ifstream myReadFile;
myReadFile.open("text.txt");
while (!myReadFile.eof()) {
for (int i = 0; i < 5; i++){
vector<string> tmpVec;
string tmpString;
for (int j = 0; j < 3; j++){
myReadFile >> tmpString;
tmpVec.push_back(tmpString);
}
data.push_back(tmpVec);
}
}
}
However, when I attempt to check the size of my vector in my main function, it returns the value '0'.
int main()
{
cout << data.size();
}
I think I just need a pair of fresh eyes to tell me where I'm going wrong. I feel like the issues lies within the createVector function, although I'm not 100% sure.
Thank you!
You should use std::getline to get the line of data first, then extract each string from the line and add to your vector. This avoids the while -- eof() issue that was pointed out in the comments.
Here is an example:
#include <string>
#include <iostream>
#include <vector>
#include <sstream>
typedef std::vector<std::string> StringArray;
std::vector<StringArray> data;
void createVector()
{
//...
std::string line, tempStr;
while (std::getline(myReadFile, line))
{
// add empty vector
data.push_back(StringArray());
// now parse the line
std::istringstream strm(line);
while (strm >> tempStr)
// add string to the last added vector
data.back().push_back(tempStr);
}
}
int main()
{
createVector();
std::cout << data.size();
}
Live Example
I have a txt file with a lot of things in it.
The lines have this pattern: 6 spaces then 1 int, 1 space, then a string.
Also, the 1st line has the amount of lines that the txt has.
I want to put the integers in an array of ints and the string on an array of strings.
I can read it and put it into an array , but only if I'm considering the ints as chars and putting into one array of strings.When I try to separate things I have no idea on how I'd do it. Any ideas?
The code I used for putting everything in an array was this:
int size()
{
ifstream sizeX;
int x;
sizeX.open("cities.txt");
sizeX>>x;
return x;
};
int main(void)
{
int size = size();
string words[size];
ifstream file("cities.txt");
file.ignore(100000,'\n');
if(file.is_open())
{
for(int i=0; i<size; i++)
{
getline(file,words[i]);
}
}
}
Just to start I'm going to provide some tips about your code:
int size = size();
Why do you need to open the file, read the first line and then close it? That process can be done opening the file just once.
The code string words[size]; is absolutely not legal C++. You cannot instantiate a variable-length-array in C++. That C feature has been not included in C++ standard (some ref). I suggest you to replace with std::vector, which is more C++ code.
Here I write a snippet of function which perform what you need.
int parse_file(const std::string& filename,
std::vector<std::string>* out_strings,
std::vector<int>* out_integers) {
assert(out_strings != nullptr);
assert(out_integers != nullptr);
std::ifstream file;
file.open(filename, std::ios_base::in);
if (file.fail()) {
// handle the error
return -1;
}
// Local variables
int num_rows;
std::string line;
// parse the first line
std::getline(file, line);
if (line.size() == 0) {
// file empty, handle the error
return -1;
}
num_rows = std::stoi(line);
// reserve memory
out_strings->clear();
out_strings->reserve(num_rows);
out_integers->clear();
out_integers->reserve(num_rows);
for (int row = 0; row < num_rows; ++row) {
// read the line
std::getline(file, line);
if (line.size() == 0) {
// unexpected end of line, handle it
return -1;
}
// get the integer
out_integers->push_back(
std::stoi(line.substr(6, line.find(' ', 6) - 6)));
// get the string
out_strings->push_back(
line.substr(line.find(' ', 6) + 1, std::string::npos));
}
file.close();
return 0;
}
You can definitely improved it, but I think it's a good point where to start.
The last suggest I can give you, in order to improve the robustness of your code, you can match each line with a regular expression. In this way you can be sure your line is formatted exactly how you need.
For example:
std::regex line_pattern("\\s{6}[0-9]+\\s[^\\n]+");
if (std::regex_match(line, line_pattern) == false) {
// ups... the line is not formatted how you need
// this is an error
}
I am trying to replace arrays with vectors but I can't figure out how.
Replace this function to dynamically allocate memory for vectors:
string readFile(string filename, string** list, int size){
*list = new string[size];
ifstream file(filename);
string line;
for (int i = 0; i < size; i++){
getline(file, line);
*(*list + i) = line;
}
file.close();
return **list;
}
And here's my attempt to change it to vectors with no luck. Any feedback is greatly appreciated:
string processFile(string filename, vector<string>** list, int size){
*list = new vector<string>(size);
ifstream file(filename);
string line;
for (int i = 0; i < size; i++){
getline(file, line);
*list[i] = line; // error
}
file.close();
return **list; // error
}
You will need some proper error handling, but basically, you need neither pointers nor fixed sizes if you use containers:
std::vector<std::string> readLinesFromFile(const std::string& filename)
{
std::vector<std::string> result;
std::ifstream file(filename);
for (std::string line; std::getline(file, line); )
{
result.push_back(line);
}
return result;
}
There are several problems:
You don't need to use vector**, vector is equivalent to the list in previous code.
The return type is string, but you are returning vector**
This code should work, not tested though:
void processFile(string filename, vector<string>& list, int size){
//list = new vector<string>(size); // no need if you get a vector reference
ifstream file(filename);
string line;
for (int i = 0; i < size; i++){
getline(file, line);
list.push_back(line); //the error was because you are assigning string to a vector<string>*
}
file.close();
// you dont have to return, as vector is passed by reference
}
If you still need to use pointer of vector
void processFile(string filename, vector<string>** list, int size){
*list = new vector<string>(size); // bad practice
ifstream file(filename);
string line;
for (int i = 0; i < size; i++){
getline(file, line);
(*list)->push_back(line);
}
file.close();
// you dont have to return, as vector is passed by pointer
}
Change *list[i] = line to *list->push_back(line) and you should be okay for the first error.
The second error is going to depend on what your intent is for the return value. I think return *list->front(); will give the same result as the first example, but if you are planning on returning more than just the first line then you will need to do some concatenation. You can just create a local string and append each line as you read them.
Hopefully your teacher knows using new vector is almost always a code smell in C++ and is using this for a specific reason with a plan to fix it later.
here is a working example. enjoy :)
BTW - you don't need to pass the length, just instantiate the memory and use the push_back method.
#include <vector>
#include <fstream>
#include <string>
using namespace std;
void processFile(string filename, vector<string>** list, int size);
void main()
{
vector<string>* list = NULL;
processFile("C:\\temp.txt", &list, 13);
int i = 1;
}
void processFile(string filename, vector<string>** list, int size){
*list = new vector<string>();
ifstream file(filename);
string line;
for (int i = 0; i < size; i++){
getline(file, line);
(**list).push_back(line); // error
}
file.close();
}
I have a .txt parameter file like this:
#Stage
filename = "a.txt";
...
#Stage
filename = "b.txt";
...
Basically I want to read one stage each time I access the parameter file.
I planed to use getline in C++ with delimiter "#Stage" to do this. Or there is a better way to solve this? Any sample codes will be helpful.
*struct content{
DATA data;
content* next;
};
struct List{
content * head;
};
static List * list;
char buf[100];
FILE * f = fopen(filename);
while(NULL != fgets(buf,f))
{
char str[100] ={0};
sccanf(buf,"%s",str);
if(strcmp("#Stage",str) == 0)
{
// read content and add to list
cnntent * p = new content();
list->add();
}
else
{
//update content in last node
list->last().data =
}
}*
Maybe I should express more clear. Anyway, I manage like this:
ifstream file1;
file1.open(parfile, ios::binary);
if (!file1) {
cout<<"Error opening file"<<parfile<<"for read"<<endl;
exit(1);
}
std::istreambuf_iterator<char> eos;
std::string s(std::istreambuf_iterator<char>(file1), eos);
unsigned int block_begin = 0;
unsigned int block_end = string::npos;
for (unsigned int i=0; i<stage; i++) {
if(s.find("#STAGE", block_begin)!=string::npos) {
block_begin = s.find("#STAGE", block_begin);
}
}
if(s.find("#STAGE", block_begin)!=string::npos) {
block_end = s.find("#STAGE", block_begin);
}
string block = s.substr(block_begin, block_end);
stringstream ss(block);
....
I'd read line by line, ignoring the lines, starting with # (or the lines, with content #Stage, depending on the format/goal) (as there's no getline version, taking std::string as delimiter).