How to sort files by modified date in iOS

Question

I used NSFileManager to retrieve the files in a folder, and I want to sort them by modified date. How to do that ?

Thanks.

Answer 1

What have you tried so far?

I haven't done this, but a quick look at the docs makes me think that you should try the following:

1. Call -contentsOfDirectoryAtURL:includingPropertiesForKeys:options:error: and specify NSURLContentModificationDateKey as one of the keys.
2. You'll get back an array of NSURL objects which you can then sort using an NSArray method like -sortedArrayUsingComparator:.
3. Pass in a comparator block that looks up the modification date for each NSURL using -getResourceValue:forKey:error:.

Update: When I wrote the answer above, -getResourceValue:forKey:error: existed in iOS but didn't do anything. That method is now functional as of iOS 5. The following code will log an app's resource files followed by a list of corresponding modification dates:

NSFileManager *manager = [NSFileManager defaultManager];
NSArray *files = [manager contentsOfDirectoryAtURL:[[NSBundle mainBundle] resourceURL]
                        includingPropertiesForKeys:[NSArray arrayWithObject:NSURLContentModificationDateKey]
                                           options:nil
                                             error:nil];
NSMutableArray *dates = [NSMutableArray array];
for (NSURL *f in files) {
    NSDate *d = nil;
    if ([f getResourceValue:&d forKey:NSURLContentModificationDateKey error:nil]) {
        [dates addObject:d];
    }
}
NSLog(@"Files: %@", files);
NSLog(@"Dates: %@", dates);