I'm replicating the TextQuery example in C++ Primer 5th edition. The code compiles, but it keeps throwing "read access violation" from Vector header when a push_back operation is executed. Here's my code (* is the line with bug):
//main.cpp
#include "stdafx.h"
using namespace std;
int main()
{
ifstream ifile;
ifile.open("D:/OneDrive/Learning/C++/ConsoleApplication1/ConsoleApplication1/testfile.txt");
runQueries(ifile); //*
// ...
}
//stdafx.h
#pragma once
#include "targetver.h"
#include <stdio.h>
#include <tchar.h>
#include <vector>
#include <string>
#include <memory>
#include <iostream>
#include <algorithm>
#include <fstream>
#include <iterator>
#include <sstream>
#include <map>
#include <set>
#include "TextQuery.h"
//TextQuery.h
void runQueries(ifstream &infile)
{
TextQuery tq(infile); //*
// ...
}
class TextQuery {
public:
using line_no = std::vector<std::string>::size_type;
TextQuery(std::ifstream&); //*
// ...
private:
std::shared_ptr<std::vector<std::string>> file;
std::map < std::string, std::shared_ptr<std::set<line_no>>> wm;
};
TextQuery::TextQuery(std::ifstream &is)
{
string text;
while (getline(is, text)) {
file->push_back(text); //*
//...
}
}
The next execution will raise an exception in vector header:
bool _Has_unused_capacity() const _NOEXCEPT
{ // micro-optimization for capacity() != size()
return (this->_Myend() != this->_Mylast());
}
Here's the error message:
Exception thrown: read access violation.
std::_Vector_alloc<std::_Vec_base_types<std::basic_string<char,std::char_traits<char>,std::allocator<char> >,std::allocator<std::basic_string<char,std::char_traits<char>,std::allocator<char> > > > >::_Myend(...) returned 0xC.
Here's the text file I used for testing:
//text file
text is good
text is good
text is good
text is good
text is good
text is good
text is good
text is good
text is good
As pointed out by #molbdnilo: I forgot to allocate "file".
After changing the constructor to the following, the problem is solve:
TextQuery::TextQuery(std::ifstream &is):file(new vector<string>)
{
string text;
while (getline(is, text)) {
file->push_back(text); //*
//...
}
}
Related
So I am very new to C++ and I am having a hard time learning how too implement classes into a function I have. My prof isn't being helpful in any capacity and I am very lost.
So the jist of the program is to take a file "books.txt" where each line contains an author and a book in the following format: Douglas Adams, The Hitchhiker's Guide to the Galaxy
I am trying to get the function to populate an array with "Book" objects with the title and author data from the file. It takes 4 input arguments: a name of the file as a string, an array of "Book" objects, the number of "Book" objects stored in the array of Book, and the capacity of the library system (with a max of 200).
For each line in the file, I am supposed to instantiate a Book object, fill in the author and title data members (listed in the code below), and append the object to the array of "Book" objects and it will return the numbers of books in the system as an integer.
Here is my header file (Book.h):
#include <iostream>
#include <math.h>
#include <string>
#include <string.h>
#include <fstream>
#include <stdio.h>
#include <cctype>
#include <locale>
#include <algorithm>
using namespace std;
#ifndef BOOK_H
#define BOOK_H
class Book{
private: //Member Variables
string author;
string title;
string inauthor;
string intitle;
string input;
string input2;
public:
Book();
Book(string intitle, string inauthor);
string getTitle();
void setTitle(string input);
string getAuthor();
void setAuthor(string input2);
};
#endif
Here is the .cpp file associated with the header file:
#include <iostream>
#include <math.h>
#include <string>
#include <string.h>
#include <fstream>
#include <stdio.h>
#include <cctype>
#include <locale>
#include <algorithm>
#include "Book.h"
using namespace std;
//Default constructor
Book::Book(){
author = "";
title = "";
}
//Parameterized Constructor
Book::Book(string intitle, string inauthor){
}
//An accessor function that returns the name of the title
string Book::getTitle() {
return title;
}
//A function that assigns the value title to the input given by the user
void Book::setTitle(string title){
title = intitle;
}
//An accessor function that returns the name of the author
string Book::getAuthor() {
return author;
}
//A function that assigns the value author to the input given by the user
void Book::setAuthor(string author){
author = inauthor;
}
And finally, here is the function I am trying to place it into (it is incomplete as every previous attempt I have made to use classes ends in a long list of errors and here is where I can confidently say I can get to):
#include <iostream>
#include <math.h>
#include <string>
#include <string.h>
#include <fstream>
#include <stdio.h>
#include <cctype>
#include <locale>
#include <algorithm>
#include "Book.h"
#include "User.h"
using namespace std;
int readBooks (string filename, int books[] , int bookObj, int capacity){
int i = 0;
ifstream file;
file.open (filename);
if (file.fail()){
return -1;
}
else{
string line;
while ((i < books) && (i < capacity) && (getline(file,line))){
}
}
I bet this is probably a very simple problem but neither the book or any other resources I have been referencing has been able to help me very much. Any help or advice would be greatly appreciated! Thank you!
I can help you out with your class design. It would look something like this:
Book.h
#ifndef BOOK_H
#define BOOK_H
#include <string>
#include <vector>
const int LIBRARY_MAX_CAPACITY = 200;
class Book {
private:
std::string author_;
std::string title_;
public:
Book() : author_( "" ), title_( "" ) {}
Book( const std::string& authorIn, const std::string& titleIn ) :
author_( authorIn ), title_( titleIn )
{}
void setAuthor( const std::string& authorIn ) {
this->author_ = authorIn;
// or just author_ = authorIn;
}
void setTitle( const std::string& titleIn ) {
this->title_ = titleIn;
// or just title_ = titleIn;
}
std::string getAuthor() const { return author_; }
std::string getTitle() const { return title_; }
};
void readBooks( const std::string& filename, std::vector<Book>& books );
#endif // BOOK_H
Book.cpp
#include "Book.h"
#include <fstream>
// this is just pseudo code and will not actually compile
void readBooks( const std::string& filename, std::vector<Book>& books ) {
// open file, test if open correctly
std::ifstream file;
file.open( filename );
// loop through file until end is reached by reading in
// a line of code and getting the contents of the book
while ( file still has data && line <= LIBRARY_MAX_CAPACITY ) {
// get a line of text then parse that line of text.
std::string author = "first string from file before comma"
std::string title = "second string from file after comma"
// create a book object here:
Book book( author, title );
// push back into vector that is passed into this function by reference
books.push_back( book );
}
// done with loop close the file
file.close();
}
Now what ever other function calls this function such as main, or your Library class etc. The std::vector<Book> object will be passed back by reference that is already populated with book objects and std::vector<> has a .size() function that returns it's size as an std::size_t.
After writing my header file and trying to use it in the cpp.file. The compiler gives me an error when trying to redefine the function in header file.
I didn't face this problem the previous times I was using headers in a similar way. Maybe I initialize the Vector in a wrong way. Anyways here is the code:
#include <string>
#include <vector>
#include "lajitellut.h"
using namespace std;
namespace otecpp_lajitellut{
/*this is where the error appears*/
vector<string> lajitellut(int lkm, char*mjt[]){
vector<string> stringVector;
for(int i =0; i<lkm; i++){
stringVector.push_back(mjt[i]);
}
for(int i =0; i<lkm; i++){
for(int a = 0; a<lkm;a++){
if(stringVector[i] < stringVector[a]){
stringVector[i].swap(stringVector[a]);
}
}
}
return stringVector;
}
}
And here is the header file
#ifndef kissa
#define kissa
#include <string>
#include <vector>
namespace otecpp_lajitellut{
std::vector <std::string> lajitellut(int lkm, char* mjt[]) {
std::vector<std::string> stringVector;
return stringVector;
}
}
#endif // kissa
Put only the function declaration in the "lajitellut.h" header file:
#include <vector>
#include <string>
namespace otecpp_lajitellut {
std::vector<std::string> lajitellut(int, char*);
}
Put the function definition in the source "*.cpp" file:
#include <iostream>
#include <vector>
#include <string>
#include "lajitellut.h"
namespace otecpp_lajitellut {
std::vector<std::string> lajitellut(int lkm, char* mjt[]) {
// your code in here
}
}
int main(){
auto a = otecpp_lajitellut::lajitellut(10, "asd");
}
Note that definition is also a declaration. That being said you don't have a vector there. You have a function of type std::vector<std::string>. Don't use using namespace std;.
Ron is right.
Your function lajitellut() is already implemented in the .h file with the same signature. You can not create a double in the same namespace.
You can change the arguments or the type of the return value or change the namespace in the .cpp file.
Error: multiple definition of `GameKey::getGameKeywords()'
GameKey.cpp and .h cause error, while ExitKey.cpp and .h are essentially the exact same class and header but do not produce an error.
(I know the whole thing about using namespace std)
//Function Declarations
#ifndef GAMEKEY_H
#define GAMEKEY_H
// C++ libraries
#include <iostream>
#include <fstream>
#include <string>
#include <vector>
#include <iterator>
#include <algorithm>
using namespace std;
class GameKey
{
private:
string keyString;
string lineData;
public:
// Default constructor
GameKey();
// Deconstructor
~GameKey();
// Get keywords
string getGameKeywords();
};
#endif
GameKey.cpp
//Function Definitions
#include "GameKey.h"
// Constructor
GameKey::GameKey()
{
}
// Deconstructor
GameKey::~GameKey()
{
}
// Get keywords
string GameKey::getGameKeywords()
{
ifstream infile;
infile.open("GameKey.txt");
while (getline(infile, lineData))
{
keyString.append(lineData);
keyString.append("\n");
}
infile.close();
return keyString;
}
ExitKey.h
//Function Declarations
#ifndef EXITKEY_H
#define EXITKEY_H
// C++ libraries
#include <iostream>
#include <fstream>
#include <string>
#include <vector>
#include <iterator>
#include <algorithm>
using namespace std;
class ExitKey
{
private:
string keyString;
string lineData;
public:
// Default constructor
ExitKey();
// Deconstructor
~ExitKey();
// Get keywords
string getExitKeywords();
};
#endif
ExitKey.cpp
//Function Definitions
#include "ExitKey.h"
// Constructor
ExitKey::ExitKey()
{
}
// Deconstructor
ExitKey::~ExitKey()
{
}
// Get keywords
string ExitKey::getExitKeywords()
{
ifstream infile;
infile.open("ExitKey.txt");
while (getline(infile, lineData))
{
keyString.append(lineData);
keyString.append("\n");
}
infile.close();
return keyString;
}
Thanks for any help!
I think you probably include GameKey.cpp instead of GameKey.h elsewhere
I am not certain as the command used for compilation is not posted.
One possibility is repeating the file names in your compilation command could also lead to this error.
for example :-
g++ ExitKey.cpp GameKey.cpp GameKey.cpp main.cpp -o main
Hi I just started to learn C++ this week and I require some assistance.
Basically what I am trying to do is read from a .txt file and "convert" it into a vector string and then display it.
my error is at this line: text.readFile("scenario.txt"), it says: "request for member 'readFile' in 'text', which is of non-class type 'Conversion()'"
what does that mean?
and also my method getLines() could not be resolved.
main.cpp
#include <iostream>
#include <string>
#include <fstream>
#include <sstream>
#include <vector>
#include "Conversion.h"
using namespace std;
int main()
{
vector<string> lines;
Conversion text();
if(text.readFile("scenario.txt") == true)
lines = text.getLines();
for(int i = 0; i < lines.size(); ++i)
cout << lines[i] << endl;
return 0;
}
Conversion.cpp
#include <string>
#include <iostream>
#include <fstream>
#include <sstream>
#include <vector>
#include "Conversion.h"
using namespace std;
vector<string> lines;
Conversion::Conversion(std::vector<std::string> lines) {
lines.clear();
}
Conversion::Conversion() {
}
Conversion::~Conversion() {
}
bool Conversion::readFile(string filename) {
ifstream file;
string line;
file.open(filename.c_str());
if(!file.is_open())
return false;
while(getline(file, line))
lines.push_back(line);
return true;
}
vector<string> Conversion::getLines(){
return lines;
}
Conversion.h
#ifndef CONVERSION_H_
#define CONVERSION_H_
#include <string>
#include <iostream>
#include <fstream>
#include <sstream>
#include <vector>
class Conversion {
public:
Conversion();
Conversion(std::vector <std::string>);
~Conversion();
std::vector<std::string> getLines();
bool readFile(std::string);
private:
std::vector<std::string> lines;
std::string line;
std::ifstream file;
};
#endif
Once again, Conversion text(); is a function declaration, not a class instantiation. To call the default constructor, change it to Conversion text;
You probably wanted to copy the passed lines in your constructor:
Conversion::Conversion(std::vector<std::string> const& lines) : lines(lines) { }
Your code should work now, but there can be done some improvements. To avoid copy, getLines should return by reference-to-const:
std::vector<std::string> const& getLines();
// you don't have to create lines in main, you can print like this:
for(auto const& x : text.getLines())
cout << x << endl;
and I'd use it even here:
bool readFile(std::string const&);
I hope this is the last thing - std::ifstream constructor and open function also take std::string:
file.open(filename);
You need to remove the parentheses when instantiating the Conversion object:
Conversion text;
See this question for detailed answers: Is no parentheses on a constructor with no arguments a language standard?
I've got the problem with following code. It should get the object parameters from the txt file. Of course to get enum values correctly I've made this simple getline() function. I'm keep getting errors which I've tried to repair, but I still have no idea what's wrong. VC says that 'no instance of overloaded function getline matches the argument list'.
My code:
CKomputer.cpp
#include <iostream>
#include <cstdio>
#include <string>
#include <fstream>
#include "CKomputer.h"
#include "Procesor.h"
#include "KartaDzwiekowa.h"
#define TESTPR1
using namespace std;
void Komputer::pobierz(string nazwa)
{
#ifdef TESTPR1
cout<<"Uruchomiono metode pobrania stanu obiektu Komputer z pliku"<<endl;
#endif
ifstream plik_wejsciowy;
plik_wejsciowy.open(nazwa+".txt");
int zastos;
getline(plik_wejsciowy,linia);
zastos=atoi(linia.c_str());
zastosowanie=Komputer::zastosowanie(zastos);
plik_wejsciowy >> nazwa_komputera >> ram >> ile_kart_dzwiekowych >> zastos;
procesor.wczytaj(plik_wejsciowy);
if (ile_kart_dzwiekowych>0)
{
for (int i=0;i<ile_kart_dzwiekowych;i++)
karta_dzwiekowa[i].wczytaj(plik_wejsciowy);
}
plik_wejsciowy.close();
}
CKomputer.h
#pragma once
#include <stdlib.h>
#include <iostream>
#include <string>
#include <fstream>
#include "UrzadzenieElektroniczne.h"
#include "Procesor.h"
#include "KartaDzwiekowa.h"
using namespace std;
enum zastosowanie{biznes, gaming, grafika, programowanie};
class Komputer: public UrzadzenieElektroniczne
{
private:
Procesor procesor;
KartaDzwiekowa *karta_dzwiekowa;
protected:
string nazwa_komputera;
int ram;
int ile_kart_dzwiekowych;
public:
Komputer();
Komputer(string nazwa_komputera2, int ram2, int ile_kart_dzwiekowych2);
Komputer(const Komputer& k);
Komputer(int ilosc_kart);
~Komputer();
static int ile_Komputerow;
static int licz_ile_Komputerow();
void komp_info();
void wlaczenieurz();
void zapisz(string nazwa);
void pobierz(string nazwa);
zastosowanie zastos;
};