Re: "inFile" object cannot read EOF
On Jun 7, 8:52 pm, waltbrad <waltb...@hotmail.com> wrote:
Hello. I'm studying the book "C++ Primer Plus" by Stephan Prata. In
chapter 6 he gives an exercise that reads from a file. The list is
thus:
4
Sam Stone
2000
Freida Flass
100500
Tammy Tubbs
5000
Rich Raptor
55000
So I create a istream object, inFile, and associate the file with
it. I know it reads the file because I've placed cout directives
after every read instruction. (since taken out). But I can't get the
program to read EOF.
You can't "read" EOF, since by definition, a read fails if the
file is at EOF. You have to try to read something, and then
check whether it failed. After failure, you can check whether
it was due to EOF, or some other reason.
After the following code there are conditions that test for
inFile.eof() and inFile.fail() but these get skipped over, to a
default "else" condition.
I would help if you'd show them, however...
Can anyone see why EOF is not being recognized?
inFile >> size;
donor *pd = new donor[size];
while(inFile.get() != '\n')
;
Why not simply: inFile.ignore( INT_MAX, '\n' ) ?
More generally, your file is line oriented, so it is probably
better to read it line by line, using an istringstream to
convert the numeric values (and verifying that the format is
correct). So the above would read:
std::string line ;
if ( ! std::getline( inFile, line ) ) {
// Error, file was empty...
}
std::istringstream sLine( line ) ;
if ( ! (sLine >> size >> std::ws) || sLine.get() != EOF ) {
// Error, first line didn't contain a number, or
// had extra junk at the end...
}
Given that your format includes lines with just a single number,
I'd probably wrap this into a separate function.
Finally, there's no reason in C++ to have to specify the count
at the start. Just use std::vector, and push_back until you
encounter end of file.
for(int i = 0; i < size; i++){
getline(inFile, pd[i].name); //a cout stmt here and
inFile >> pd[i].cash; //here lets me know the data was
read
while(inFile.get() != '\n')
;
}
I'd write this loop something like:
std::vector< donor > donors ;
std::string line1 ;
std::string line2 ;
while ( getline( inFile, line1 ) && getline( inFile, line2 ) ) {
double cash ;
std::istringstream sCash( line2 ) ;
sCash >> cash ;
donors.push_back( donor( line1, cash ) ) ;
}
Except, of course, that it requires more error handling; the
above only works if the file has the correct format.
--
James Kanze (GABI Software) email:james.kanze@gmail.com
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