i'm trying to pass a string from main to another function. this string is a name of text file that needs to be oepened. as far as i can see, i am passing the string alright, but when i try to use ifstream.open(textFileName)
, it doesn't quite work. but when i manually hardcode it as ifstream.open("foo.txt")
, it works just fine. i would need to use this function several times so i would like to be able to pass in a string of text file name..
here's my main
#ifndef DATA_H
#define DATA_H
#include "Data.h"
#endif
#ifndef DATAREADER_H
#define DATAREADER_H
#include "DataReader.h"
#endif
using namespace std;
int main()
{
vector<Data*> database = DataReader("foo.txt");
return 0;
}
header of DataReader
#include <fstream>
#include <iostream>
#include <vector>
#include <string>
#ifndef DATA_H
#define DATA_H
#include "Data.h"
#endif
using namespace std;
vector<Data*> DataReader(string textFile);
and finally the DataReader.cpp
#include "DataReader.h"
using namespace std;
vector<Data*> DataReader(string textFile)
{
ifstream aStream;
aStream.open(textFile); //line 11
i looked up the ifstream.open() and it takes a string and a mode as parameters. not really sure what to do with the modes, but i tried them but they gave the same error message
DataReader.cpp: In function 'std::vector<Data*, std::allocator<Data*> > DataReader(std::string)':
DataReader.cpp:11: error: no matching function for call to 'std::basic_ifstream<char, std::char_traits<char> >::open(std::string&)'
/usr/local/lib/gcc/sparc-sun-solaris2.9/4.0.3/../../../../include/c++/4.0.3/fstream:495: note: candidates are: void std::basic_ifstream<_CharT, _Traits>::open(const char*, std::_Ios_Openmode) [with _CharT = char, _Traits = std::char_traits<char>]
thank you in advance for any input/suggestions.
Dean
Read whole ASCII file into C++ std::string txt using file object f of ifstream type to perform read operation. Declare a variable str of string type. If(f) Declare another variable ss of ostringstream type. Call rdbuf() fuction to read data of file object.
The C++ string class is defined in a library file named "string." If you want to use variables or parameters of type string in a program, you should add the line "#include <string>" at the beginning of the program.
The ifstream Class. An ifstream is an input file stream, i.e. a stream of data used for reading input from a file. Because an ifstream IS an istream, anything you can do to an istream you can also do the same way to an ifstream.
the standard streams doesn't accept a standard string
, only c-string
! So pass the string using c_str()
:
aStream.open(textFile.c_str());
Try this:
aStream.open(textFile.c_str()); //line 11
I think your code needs to take the internal C string to pass to the open() call. Note I'm not at a compiler right now, so can't double check this.
You may also want to check the signature of the this method:
vector<Data*> DataReader(string textFile);
Here, a complete copy of the vector will be taken when it's returned from the method, which could be computationally expensive. Note, it won't copy the Data objects, just the pointers, but with a lot of data might not be a good idea. Similarly with the string input.
Consider this instead:
void DataReader( const string& textFile, vector<Data*>& dataOut );
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