Coping folder contents and sub folders

Question

So, I'm working on a little practice folder sync project (fun with my mac)...
...and I'v gotten hung up a bit because my little copying app doesn't seem to count folders and sub folders (which I suppose makes sense).
My initial idea was to take just the date of modification and compare it to the last date that the app was run, inorder to only copy changed files. But this seems problematic on a few levels, so...
So, my two part question is:
1. Is there a simple command to copy folder contents and sub-folder contents, or do I need to tell the script to do each sub-folder individually?
2. I imagine that a better way to manage which files/folders need to be updated is to create a file with a list of the contents, and dates of modification, and compare the new folder list and the old folder list to each-other... ok.. so, um. yeah. that sounds tricky.

Answer 1

>1. Is there a simple command to copy folder contents and sub-folder contents, or do I need to tell the script to do each sub-folder individually?
There are two common solutions to this.
The first is to use the Finder's 'entire contents of...' command to get a list of everything in the folder, including sub-folders, the second is to make your script recursive - that is, it calls itself several times over.
In the first case it's as simple as:
tell application "Finder"
set allItems to entire contents of folder "path:to:source:folder:"
-- rest of code goes here
end tell
This can have problems, though, especially on very large directories since the Finder is not very efficient at building a list of hundreds or thousands of files.
The recursive path is a little trickier, but you write a handler to process a folder then repeatedly call that handler, like:
<pre class=command>on run
set sourceFolder to (choose folder)
processAFolder(sourceFolder)
end run
on processAFolder(theFolder)
tell application "Finder"
set allItems to items of folder theFolder as alias list
repeat with eachItem in allItems
if class of eachItem is folder then -- we have a subfolder
processAFolder (eachItem)
else
-- code here to compare the file and back it up
end if
end repeat
end tell
end processAFolder</pre>
So here you walk through the folder, each time you find a new folder, you walk through that until you're done. The code takes care of keeping track of where you are in the folder hierarchy.
>2. I imagine that a better way to manage which files/folders need to be updated is to create a file with a list of the contents, and dates of modification, and compare the new folder list and the old folder list to each-other... ok.. so, um. yeah. that sounds tricky.
There's no need to keep a file. Assuming you have two folders you can just walk through one of them checking to see if each item exists in the other, then copy the newer file to the other directory, like:
<pre class=command>on processAFile(fileName, sourceDir, destDir)
tell application "Finder"
-- check if the files exist
set sourceFileExists to (file fileName of folder sourceDir exists)
set destFileExists to (file fileName of folder destDir exists)
-- now comes the logic
if sourceFileExists and not destFileExsits then
duplicate file fileName of folder sourceDir to folder destDir
else if destFileExists and not sourceFileExists then
-- assuming you want a two-way synch
duplicate file fileName of folder destDir to folder sourceDir
else -- both files exist, so check mod dates
if (modification date of file fileName of folder sourceDir) > (modification date of file fileName of folder destDir) then
duplicate file fileName of folder sourceDir to folder destDir
else if (modification date of file fileName of folder destDir) > (modification date of file fileName of folder sourceDir) then
duplicate file fileName of folder sourceDir to folder destDir
end if
end if
end tell
end processAFile</pre>
If you're not planning a two-way synch an even simpler option is to just keep track of the last time the synch was run. Then all you need to do on subsequent runs is ask the Finder for 'every file of folder sourceFolder whose modification date is greater than lastRunDate'.