Hi Udo, that’s a very detailed explanation, thanks for taking the time to write it!
> On May 7, 2016, at 05:46, Udo Schneider <udo.schnei...@homeaddress.de> wrote: > > Hi Johan, > > I remember running into similar problems because I didn't understand the > FileSystem philosophy ... and dealing with strings and concatenating them is > so much easier, right? :-) > > After reading the chapter on FileSystem several times over and over again the > IMHO most important part of it to get the grasp of FileSystem is on page 13 > (http://pharobooks.gforge.inria.fr/PharoByExampleTwo-Eng/latest/FileSystem.pdf): > > " > FileReference = FileSystem + Path > Paths and filesystems are the lowest level of the FileSystem API. A > FileReference combines a path and a filesystem into a single object which > provides a simpler protocol for working with files as we show in the previous > section. References implement the path protocol with methods like /, parent > and resolve:. > " > > So in your example ‘/home/jfabry’ and ‘test/code/foo.txt’ are just (relative) > path strings. They do not reference anything outside of the context of a > filesystem. The hard part for me to understand was the fact that a path may > not be unique. The same path might reference different files in different > filesystems. > This is especially strange coming from a *nix background where there is only > one filesystem. > But even on Windows one could argue that the OS nowadays only knows one > filesystem: You can reference any file via a UNC path ... drives, shares, > partitions, URIs and other filesystems are simply aliases into the UNC space. > The nice thing of the FileSystem API is it's ability to transparently use > files in-Memory, archives, FTP, WebDav, S3 ... . All from within Pharo with > the same consistent API. E.g. if you have the FileSystemNetwork > (http://smalltalkhub.com/#!/~UdoSchneider/FileSystemNetwork) installed you > can do something like: > > > > "Obtain a FTP FileSystem" > fs := FileSystem ftp: 'ftp://ftp.2600.com'. > > "Get working directory" > wd := fs workingDirectory . > > "Print the following expression!" > (wd / 'pub' / 'publications' / 'n0way') children. > (wd / 'pub' / 'publications' / 'n0way' / 'README') contents. > > "Open a FileList on the FileSystem" > FileList openOn: wd. > > "Remember to close if you are finished!" > fs close. > > > > > So to make a long story short: Both your strings contain paths. So we have to > convert them into Paths and somehow combine them with a FileSystem to get a > valid FileReference: > > > > "I changed the second string to demonstrate dealing with different delimiters" > dirString := '/home/jfabry'. > fileString := 'test\code\foo.txt'. > > "Convert path strings to Paths" > dirPath := Path from: dirString delimiter: $/. > filePath := Path from: fileString delimiter: $\. > "Please note the Paths do not reference anything. We have no FileSystem > context yet" > > "The FileSystem our Paths will be resolved within" > diskFs := FileSystem disk. > > "FileReference for the root directory in the FS" > rootRef := diskFs root. > > "Resolve our Paths in the Context of the Reference" > dirRef := rootRef resolve: dirPath. > fileRef := dirRef resolve: filePath. "File @ /home/jfabry/test/code/foo.txt" > > "Please note the fileRef printString. 'File' denotes the FileSystem - not the > fact that this is a file! Then you have the path after the at sign" > > > > > > I hope this helps. > > Final advice: In Pharo you should *never never never* assume that a Path is > "enough" to reference a file. You will always need the context (it's > FileSystem) as well. And that's exactly what a FileReference (see above) is. > So if you only have a Path it's questionable to assume that you can simply > combine it with a DiskFileSystem to get a valid reference. What if the Path > references a file in a ZIP in-Memory archive? Trying to access the Path on > disk will yield no result. So always always always store/pass a FileReference > if possible!!!! > I did run into that issue in the past with archive/net FileSystems where some > dev tools at one point extracted the Path from the FileReference and passed > them arround. Down the stack some other methods needed the file contents. > Because only the Path was passed they assumed they could retrieve the > contents by simply combining it with a DiskFileSystem ... and boom! > > > CU, > > Udo > > > On 07/05/16 00:33, Johan Fabry wrote: >> Hi all, >> >> I have a question about the filesystem that I could not resolve using the >> documentation. The problem is as follows: I have a file reference that is 2 >> separate strings that I need to join into one complete file ref but I don’t >> know how because I don’t know what the platform’s file separator is. >> >> For example, on a unix-like OS I get ‘/home/jfabry’ as one part and >> ‘test/code/foo.txt’ as the other part, and I need to construct a >> FileReference to ‘/home/jfabry/test/code/foo.txt’.On M$ I guess this would >> be 'C:\users\jfabry' and ‘test\code\foo.txt’, so I need to construct >> FileReference to 'C:\users\jfabry\test\code\foo.txt’ >> >> And the bingo question is: what do I do if I both strings use different >> kinds of separators? >> >> TIA, >> >> ---> Save our in-boxes! http://emailcharter.org <--- >> >> Johan Fabry - http://pleiad.cl/~jfabry >> PLEIAD and RyCh labs - Computer Science Department (DCC) - University of >> Chile >> >> >> > > > > ---> Save our in-boxes! http://emailcharter.org <--- Johan Fabry - http://pleiad.cl/~jfabry PLEIAD and RyCh labs - Computer Science Department (DCC) - University of Chile
