boost filesystem version 3 issue? - c++

Question

the example code on the boost website is not working. http://www.boost.org/doc/libs/1_46_1/libs/filesystem/v3/doc/tutorial.html#Using-path-decomposition
int main(int argc, char* argv[])
{
path p (argv[1]); // p reads clearer than argv[1] in the following code
try
{
if (exists(p)) // does p actually exist?
{
if (is_regular_file(p)) // is p a regular file?
cout << p << " size is " << file_size(p) << '\n';
else if (is_directory(p)) // is p a directory?
{
cout << p << " is a directory containing:\n";
typedef vector<path> vec; // store paths,
vec v; // so we can sort them later
copy(directory_iterator(p), directory_iterator(), back_inserter(v));
sort(v.begin(), v.end()); // sort, since directory iteration
// is not ordered on some file systems
for (vec::const_iterator it (v.begin()); it != v.end(); ++it)
{
path fn = it->path().filename(); // extract the filename from the path
v.push_back(fn); // push into vector for later sorting
}
}
else
cout << p << " exists, but is neither a regular file nor a directory\n";
}
else
cout << p << " does not exist\n";
}
catch (const filesystem_error& ex)
{
cout << ex.what() << '\n';
}
return 0;
}
two error messages when compiled in visual studio 2010 for the line path fn = it->path().filename();
The first error is: 'function-style cast' : illegal as right side of '->' operator and the second error is: left of '.filename' must have class/struct/union
Also, when I mouse over path() it says: class boost::filesystem3::path Error: typename not allowed

Answer 1

This section (for's body) is problematic:
path fn = it->path().filename(); // extract the filename from the path
v.push_back(fn); // push into vector for later sorting
it points to path objects, so I don't see why path() is called. Seems that it should be replaced with it->filename()
you push filenames at the end of the same vector, so after the loop you will have the vector containing the list of files twice, first with pathnames then just filenames.
EDIT: Looking at the original example I see that these are your modification. If you want to store filenames instead of printing them, define another vector of string or path and store filenames in it, don't reuse the first one. And removing the call to path() should solve the compilation problem.
EDIT 2: as a cute BTW, you can achieve both directory traversal and filename extraction in one pass using std::transform instead of std::copy:
struct fnameExtractor { // functor
string operator() (path& p) { return p.filename().string(); }
};
vector<string> vs;
vector<path> vp;
transform(directory_iterator(p), directory_iterator(), back_inserter(vs),
fnameExtractor());
Same using mem_fun_ref instead of fnameExtractor functor:
transform(directory_iterator(p), directory_iterator(), back_inserter(vp),
mem_fun_ref(&path::filename));

Answer 2

After you posted the link it seems that the code posted is working fine. But problem is introduced in the modified code in for loop. 1st problem is that, path() is a constructor. 2nd problem, I am not sure about boost::path contains any method as filename(). You can try,
path fn = (*it);