Hi Damien, On Fri, Mar 30, 2018 at 05:30:52PM +0200, Damien Pollet wrote:
I understand that when you want to actually open and read/write files, you have to resolve them in a filesystem and that's what a FileReference is for.
But there are uses for file paths BEFORE you have a filesystem to resolve them in.
I was talking about a config file, in which some values are file names (sometimes absolute paths, sometimes relative). In a config file the paths are not resolved because the filesystem is not known; maybe I want to test the config file parser, and I don't actually have the matching files, or maybe they are in a memory filesystem.
Maybe I'm reading a Zip archive and I'm specifying a member of the archive (so the path does not point to an actual file on disk).
FileReferences are designed to handle this situation, e.g. Let's say I've zipped up my pharo directory: (FileSystem zip: 'pharo.zip' asFileReference) open / 'pharo-local/play-cache/2018-03-29T21-49-20-403605+02-00.ph' is perfectly fine. Sending #contents to the resulting FileReference will give me the expected result.
Maybe I'm writing a command-line argument parser, and some arguments are supposed to be file paths and I want to syntactically validate that aspect. Or I want to ensure that an argument is relative and not absolute. Or the argument is a relative path from an implicit origin (unspecified as far as the commandline parser is concerned); because the origin will be determined by application code.
Good point. FileSystem was written long before I got involved with Pharo, so I don't know whether this situation was considered, and what the expected approach was. It would still be possible to use a FileReference to do the check - there's nothing that says the path has to exist. However that does seem to be stretching the usage, so I agree that using Path makes sense in this case.
In all those use cases, using FileReferences is just incorrect, as we're not talking about existing files, but about abstract places or navigation instructions in a hypothetical filesystem.
The comment in Path does say: "Normally users should not use me directly." So there is an out :-) I think the comment is correct though - in most cases the user should be dealing with FileReferences and not Paths. Cheers, Alistair
On 30 March 2018 at 16:57, Alistair Grant <akgrant0710@gmail.com> wrote:
Hi Damien,
On 30 March 2018 at 14:59, Damien Pollet <damien.pollet@gmail.com> wrote: > The class Path from FileSystem is documented as private? but it should be > public, shouldn't it? > > First hint is that it's named with a public name: (Path not FileSystemPath). > > Then, consider the following use-case : if you have a file name in some > config file (.ini, .toml?) then that's really a Path, not a resolved > FileReference.
The file name is implicitly attached to a file system, so it is resolved (using Pharo terminology). If you pass the path to a program, e.g. an editor, it has enough information to be able to open the file.
In Unix, everything is mounted on the root file system, so there's no need to specify a file system. Pharo's model allows for multiple file systems, e.g. the disk, and multiple memory and zip file systems.
Path's by themselves don't provide much functionality - you can't actually access the file or directory you think is represented by the path; you have to know which file system the path is attached to.
It's the FileReference that associates the path and the file system, and provides all the public interface.
HTH, Alistair
> I'm not talking about RelativePath and AbsolutePath, those can be hidden > away since Path provides the factory and DSL methods. IMHO they should still > be renamed to a more private name. > > -- > Damien Pollet > type less, do more [ | ] http://people.untyped.org/damien.pollet
-- Damien Pollet type less, do more [ | ] http://people.untyped.org/damien.pollet