Can I download update files from server and replace files in supporting folder? - iphone

Question

I am doing iPhone app dev. Usually, I put image(photo) files and some other configuration files in to supporting folder.
Can I update those files in supporting folder from server? If can, how to do it?
If not, can I pre-store the files which are need to upload into Document Folder and download newer files in document folder to replace older files?

Answer 1

we had the same problem in our current app. our final approach is this:
1) the assets we want to deliver with the app are stored inside a folder under Resources.
2) Plus there is an XML file telling us, which asset belongs where and how old it is (timestamp).
3) When the app starts for the first time, we copy all files (except the xml) from Rescources to the app's Cache folder:
// get the app's cache folder
NSArray *paths = NSSearchPathForDirectoriesInDomains(NSCachesDirectory, NSUserDomainMask, YES);
_cachesDirectory = [paths objectAtIndex:0];
_assetDirectory = [NSString stringWithFormat:#"%#/assets", _cachesDirectory];
// copy everything
_fmngr = [NSFileManager defaultManager];
- (void) copyAllFilesFromInitialFolder:(NSString*)path
{
NSArray *files = [_fmngr contentsOfDirectoryAtPath:path error:nil];
for (NSString *file in files)
{
if ([file isEqualToString:[NSString stringWithFormat:#"%#.xml", kDefaultXMLFileName]])
{
continue;
}
NSString *fpath = [NSString stringWithFormat:#"%#/%#", path, file];
BOOL isDir;
if ([_fmngr fileExistsAtPath:fpath isDirectory:&isDir])
{
if (isDir)
{
[self copyAllFilesFromInitialFolder:fpath];
}
else
{
NSString *relPath = [fpath substringFromIndex:[_initialLangDeviceContentPath length]+1];
NSString *fileName = [self convertFilePathToName:relPath];
NSString *tpath = [NSString stringWithFormat:#"%#/%#", _assetDirectory, fileName];
NSError *error;
BOOL success = [_fmngr copyItemAtPath:fpath toPath:tpath error:&error];
if (!success || error)
{
NSLog(#"INFO: copy %# to CACHES failed ... file may already be there.", file);
}
}
}
}
}
4) At the next start of the application, we check online if there are newer files on our update server. The XML from step 2) also resides on the server and has to be updated when JPGs/PNGs/... are updated/replaced on the server.
If nothing changed our PHP script returns a 304 "not modfied" - otherwise it'll output an updated version of the XML.
the PHP script looks something like this:
$doc = new DOMDocument();
#$doc->load($filename);
$xpath = new DOMXPath($doc);
$assets = $xpath->query('//asset');
if ($assets->length > 0)
{
foreach ($assets as $asset)
{
$assetPath = $asset->getAttribute('path');
if (file_exists($assetPath))
{
$atime = filemtime($assetPath);
$asset->setAttribute('modified', $atime);
}
else
{
// file not found - link broken
$asset->setAttribute('modified', '0');
}
}
}
$output = $doc->saveXML();
header('Content-type: text/xml');
echo $output;
The app downloads and parses the generated XML, comparing all modified values.
When there is an asset with a newer modified timestamp it is deleted locally and redownloaded. only after this check is completed the app starts - and you got the new assets on the device.
Hope this helps. We had some problems with the last modified attribute of the files we deliver with the app. When including the files into the app bundle and copying them at runtime, the files last modified is always the time of the first start of the app. sometimes you already updated some files on the server - but because the app thinks the files on the device are newer (because they were copied just now) they are not re-dowloaded from the server :(
so you can't work with the real file's attributes but have to include the actual file-date inside the XML file.