I know that there have been many similar questions asked as this such as:
However I have an already existing class with specific behaviors that I don't want to break and what I would like to do is to add an additional function to this class.
The current class I'm working on is a basic TextFileReader class and it inherits from a FileHandler class. I'll show the current class hierarchy so you can see what I already have: You can ignore the ExceptionHandler that is used as it is irrelevant to this question but I left it here as this is how my class is defined.
FileHandler.h
#pragma once
#include <string>
#include <sstream>
#include <fstream>
namespace util {
class FileHandler {
protected:
std::fstream fileStream_;
std::string filePath_;
std::string filenameWithPath_;
private:
bool saveExceptionInLog_;
public:
virtual ~FileHandler();
FileHandler(const FileHandler& c) = delete;
FileHandler& operator=(const FileHandler& c) = delete;
protected:
FileHandler(const std::string& filename, bool saveExceptionInLog);
void throwError(const std::string& message) const;
void throwError(const std::ostringstream& streamMessage) const;
};
} // namespace util
FileHandler.cpp
#include "FileHandler.h"
#include "ExceptionHandler.h"
using namespace util;
FileHandler::FileHandler(const std::string & filename, bool saveExceptionInLog) :
saveExceptionInLog_(saveExceptionInLog),
filenameWithPath_(filename) {
// Extract path info if it exists
std::string::size_type lastIndex = filename.find_last_of("/\\");
if (lastIndex != std::string::npos) {
filePath_ = filename.substr(0, lastIndex);
}
if (filename.empty()) {
throw ExceptionHandler(__FUNCTION__ + std::string(" missing filename", saveExceptionInLog_));
}
}
FileHandler::~FileHandler() {
if (fileStream_.is_open()) {
fileStream_.close();
}
}
void FileHandler::throwError(const std::string & message) const {
throw ExceptionHandler("File [" + filenameWithPath_ + "] " + message, saveExceptionInLog_);
}
void FileHandler::throwError(const std::ostringstream & streamMessage) const {
throwError(streamMessage.str());
}
TextFileReader.h
#pragma once
#include "FileHandler.h"
namespace util {
class TextFileReader : public FileHandler {
public:
explicit TextFileReader(const std::string& filename);
virtual ~TextFileReader() = default;
TextFileReader(const TextFileReader& c) = delete;
TextFileReader& operator=(const TextFileReader& c) = delete;
std::string readAll() const;
};
} // namespace util
TextFileReader.cpp
#include "TextFileReader.h"
using namespace util;
TextFileReader::TextFileReader(const std::string & filename) :
FileHandler( filename, true ) {
fileStream_.open(filenameWithPath_.c_str(), std::ios_base::in);
if (!fileStream_.is_open()) {
throwError(__FUNCTION__ + std::string(" can not open file for reading"));
}
}
std::string TextFileReader::readAll() const {
std::ostringstream stream;
stream << fileStream_.rdbuf();
return stream.str();
}
What I would like to do or what I'm trying to do is to add this method to my TextFileReader
std::vector<std::string> readLineByLine() const;
And I have tried several of the methods from the original Q/A's that I listed above at the beginning of this question.
Some of the issues that I have come into is that in the base class I'm storing a fstream object and not an ifstream or ofstream object so trying to use std::getline in a loop is not working. I was trying to read line by line directly from the filestream handle.
On my next attempt I tried to reuse the already existing readAll() and read all of the file's contents into a single buffer and return that back as a single string, then parse that string into a vector of strings. In this approach in my while loop I am still not able to use std::getline because it is using an ostringstream object and not an istringstream object.
The function should work something like this - pseudo code:
std::vector<std::string> TextFileReader::readLineByLine() const {
// get contents from file either line by line and store
// each line into a string and push that string into a
// vector of strings then return that vector after all
// lines have been read.
// or...
// read all contents from file into single string buffer and parse
// that string into a vector of strings and return that vector.
}
And this is where I'm having my issue. Any suggestions?
Edit
I had originally tried user's Bapo's approach but I was getting this compiler error:
1>------ Build started: Project: ChemLab, Configuration: Debug Win32 ------
1>TextFileReader.cpp
1>c:\...\textfilereader.cpp(24): error C2665: 'std::getline': none of the 2 overloads could convert all the argument types
1>c:\program files (x86)\microsoft visual studio\2017\community\vc\tools\msvc\14.16.27023\include\string(160): note: could be 'std::basic_istream<char,std::char_traits<char>> &std::getline<char,std::char_traits<char>,std::allocator<char>>(std::basic_istream<char,std::char_traits<char>> &,std::basic_string<char,std::char_traits<char>,std::allocator<char>> &)'
1>c:\program files (x86)\microsoft visual studio\2017\community\vc\tools\msvc\14.16.27023\include\string(129): note: or 'std::basic_istream<char,std::char_traits<char>> &std::getline<char,std::char_traits<char>,std::allocator<char>>(std::basic_istream<char,std::char_traits<char>> &&,std::basic_string<char,std::char_traits<char>,std::allocator<char>> &)'
1>c:\...\textfilereader.cpp(24): note: while trying to match the argument list '(const std::fstream, std::string)'
1>Done building project "ChemLab.vcxproj" -- FAILED.
========== Build: 0 succeeded, 1 failed, 0 up-to-date, 0 skipped ==========
However user one commented that if I made fileStream_ mutable the const function won't work. I went ahead and added the mutable modifier to fileStream_ member and now the function compiles.
