Recursive method not returning to previous line position in caller - ruby-on-rails

Question

I have been trying to find a solution to this for some time. I have found questions and answers on recursion but nothing that seemed to fit this particular situation.
I have written a class which should go through the given folder and all subfolders and rename files and folders if a particular search pattern is found.
Everything works as expected the replaceAllInDir gets called, it replaces files and folders if needed. The next step then is to do the same for all subfolders within the given folder.
So a subfolder gets identified and replaceAllInDir gets called from within itself. Let's assum the particular subfolder called does not contain any subfolders. I would then expect that we return to the parent folder and continue looking for other subfolders. But instead control is not returned to the parent calling method and the program ends.
I am aware of other ways of solving the actual use case, but I cannot explain the behaviour of ruby.
class MultiFileAndFolderRename
attr_accessor :rootDir, :searchPattern, :replacePattern
def initialize(rootDir, searchPattern, replacePattern)
#rootDir = rootDir
#searchPattern = searchPattern
#replacePattern = replacePattern
end
def execute
replaceAllInDir(#rootDir)
end
def getValidDirEntries(dir)
dirList = Dir.entries(dir)
dirList.delete('.')
dirList.delete('..')
dirList
end
def replaceAllInDir(currentDir)
Dir.chdir(currentDir)
puts "Processing directory: " + Dir.pwd
dirList = getValidDirEntries(currentDir)
dirList.each { |dirEntry|
attemptRename(dirEntry)
}
dirList = getValidDirEntries(currentDir)
dirList.each { |dirEntry|
if File.directory?(dirEntry)
newDir = currentDir + '\\' + dirEntry
rntemp = MultiFileAndFolderRename.new(newDir, 'searchString', 'replaceString')
rntemp.replaceAllInDir(newDir)
end
}
end
def attemptRename(dirEntry)
if dirEntry.match(#searchPattern)
newname = dirEntry.to_s.sub(#searchPattern, #replacePattern)
FileUtils.mv(dirEntry.to_s, newname)
end
end
end

Answer 1

You have a bug. The first line of replaceAllInDir() is Dir.chdir(). chdir() changes the directory of the current process on a global scale. It's not call-stack dependent. So later when you move into a subdirectory and change into that, the change becomes permanent even if you return from the recursion.
You need to change back to the correct directory after any call to replaceAllInDir(). For example:
...
dirList.each { |dirEntry|
if File.directory?(dirEntry)
....
rntemp.replaceAllInDir(newDir)
Dir.chdir(currentDir) # <- Restore us back to the correct directory
end
}

Answer 2

I have tried your code, and I have found numerous errors in it. Perhaps if you fix them, your idea is working.
You should include in a library like that a part at the end that allows to call it from the shell: MultiFileAndFolderRename.new(ARGV[0], ARGV[1], ARGV[2]).execute if __FILE__ == $0 This ensures when you call the ruby code from the shell by ruby rename.rb test old new, your class will be instantiated, and the search and replace pattern will be set accordingly.
You shouldn't set the current directory, because that ensures that the line getValidDirEntries(currentDir) will not work. If you eg. call it for the directory test, and then change your current directory to test, inside the directory, getValidDirEntries('test') will not work like expected.
You should use only forward slashes instead of the double backward ones. So your code will work on Linux and Mac OS X as well.
When you instantiate the new instance of MultiFileAndFolderRename (which is not necessary), the arguments to the initializer are the wrong ones. Instead, you should use your current instance and just call self.replaceAllInDir(newDir) instead of rntemp = MultiFileAndFolderRename.new(newDir, 'searchString', 'replaceString');rntemp.replaceAllInDir(newDir).
I think the wrong instantiation is the major reason why it works not as expected, but the others should be fixed as well.