[Boost-users] [Filesystem] v3: preferred() vs. make_preferred()

Subject: [Boost-users] [Filesystem] v3: preferred() vs. make_preferred()
From: PB (newbarker_at_[hidden])
Date: 2010-09-14 06:10:01

Hello,

I have built up a path in which the underlying string has a mixture of
slashes and backslashes. I'm passing my_path.string().c_str() to a
Windows API function which is getting confused because the string is
being provided verbatim. I'm therefore looking to convert the string.

According to the Filesystem tutorial
(http://www.boost.org/doc/libs/1_44_0/libs/filesystem/v3/doc/tutorial.html),
I can use the preferred() observer method to get the string that is
suitable for the current (Windows) platform. This sounds like quite a
nice design. However, it seems the preferred() method doesn't exist
(i.e. the tutorial is wrong). There is a make_preferred() method which
is non-const because it *changes the underlying representation* to the
format preferred by the operating system.

>From my application developer point of view, the preferred() observer
is neater/better. I don't care and don't need to know what the
underlying path format is. I have no desire to change it. All I am
bothered about is that I can store it to a string (perhaps in an
external file), and reconstruct the path from the same string. There
are a few points in the application however where I need to present
the path in a particular way, and it'd be nice to just throw a call to
preferred() there.

e.g.

listBox_.AddString(my_path.preferred().c_str());

I've now got to do:

bfs::path pref = my_path;
pref.make_preferred();
listBox_.AddString(pref.string().c_str());

because the function that does the rendering of the string to the list
box accepts the path as a const boost::filesystem::path& and therefore
cannot change it.

Wanted to point out the mismatch between the tutorial and the source
code, and am wondering on the rationale behind make_preferred() over
preferred()? Always possible I'm missing something!

Thanks,

Pete