Create a link on the ios filesystem with Objective-C

Question

I'm trying to create a comic reader app which supports both online reading & off-line reading (by downloading).

I've found MWPhotoBrowser as my image viewer, which supports SDWebImage as the image cache.

My problem is that if some user read little part of a comic on-line, and then they decides to download it for offline reading. Since the already read part is cached by SDWebImage, I don't wanna download them again from the web server. But since user asks to download them locally, I don't wanna keep them on the image cache neither as this will make the downloaded images out of our hand.

Copy the image from the image cache to the place I wanna put is a feasible solution, but it takes storage space. So, what I'm trying to do is cut the image from the image cache to the right place, and then make some soft-link in the image cache. In this way, there should be only one image copy in the storage file system.

Answer 1

You don't want a symbolic (soft) link. A symlink doesn't prevent the original file (in the cache) from being deleted. If the original file is deleted, you'll get an error when you try to open it through the symlink.

You want a hard link. You can create a hard link using -[NSFileManager linkItemAtURL:toURL:error:] or -[NSFileManager linkItemAtPath:toPath:error:]. Take a look at the NSFileManager Class Reference.

If you need to learn more about hard links and symbolic links, you can quickly find a lot of information by searching for “hard link” or “symbolic link” in your favorite search engine.

NOTE FOR FUTURE SEARCHERS

You can create a symbolic link using -[NSFileManager createSymbolicLinkAtURL:withDestinationURL:error:] or -[NSFileManager createSymbolicLinkAtPath:withDestinationPath:error:].