string manipulation

pie · March 2015

I am playing a bit with lfs, and I was wondering how to "split" a path into directories.

I found a lot of examples and snippets on how to retrieve a base directory , filenames and extensions from a given path, but I didn't find anything to "split" a path (string) as I like.

"/sdcard/dir1/banana/"   --->    "/sdcard/dir1/"     "banana/"   or --->  "/sdcard/"     "dir1/"     "banana/"

 "C:/dir1/banana/" ----> "C:/dir1/"            "banana/"    or  ---->   "C:"    "/dir1/"          "banana/"

I found about the lua string pattern, I thought I would be using string.match, but after some hours wasted on that, I think that writing patterns is something currently out of my league.. ~X(
I could really use some hint

My goal was being able to follow the directory path backwards: starting from banana to root.

Thank you

OZApps · March 2015

Hi Pie,
If you have a copy of my Book, on Page 74, there is a function that exists to split strings. It is simply 4 lines of code and are

 function string:split(sep)
  local sep, fields = sep or ":", {}
  local pattern = string.format("([^%s]+)", sep)
  self:gsub(pattern, function(c) fields[#fields + 1] = c end)
  return fields
 end

and to use it, try something like

str = ":sdcard:dir1:banana:" 
results = str:split(":")
-- You have the split data in the table.

Get the number of elements in the table via #results. Hope that helps resolve your issue.

cheers,

Jayant C Varma

Author of :
* Learn Lua for iOS Game Development, Apress
* Xcode 6 Essentials, Packt
* More iPhone Development with Swift, Apress
* More iPhone Development with Objective-C, Apress

pie · March 2015

Thank you @OzApps, I found a typo in the split function:

local pattern = string.format("([^%s]+)", sep) was missing a " )"

function string:split(sep)
  local sep, fields = sep or ":", {}
  local pattern = string.format("([^%s]+)", sep) 
  self:gsub(pattern, function(c) fields[#fields + 1] = c end)
  return fields
 end

Now it seems to work

thank you very much!

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