creating an arrays of files, sorted by modification date in objc on iphone

Huge fan of this website, but it's my first post!

I've got an array of filenames in a directory and I want to sort them. There are hundreds of posts about sorting, but I couldn't find anything I could use about sorting by modification date.

Here's my code so far. It successfully creates an array of files that feeds into my tableview. I just need to sort it by modification date, not alphabetically:

//Create dictionary with attributes I care about and a fileList array

        NSMutableArray *fileList  = [[NSMutableArray alloc] initWithCapacity:10];
        NSDictionary *fileData = [NSDictionary dictionaryWithObjectsAndKeys:file, @"file", dateString, @"date", nil];

        [fileList addObject:fileData];

//I don't know how to sort this array by the "date" key!

        NSArray         *files = [fm contentsOfDirectoryAtPath:folderPath error:NULL];
    //iterate through files array
        for (NSString *file in files) {
            NSString *path = [folderPath stringByAppendingPathComponent:file];
    //code to create custom object with contents of file as properties
    //feed object to fileList, which displays it in the tableview

I've read everything I could fi开发者_JAVA百科nd online about it, but I just don't understand how this sorting would work. I understand there are about four different ways to sort, but which one do I chose to sort the array by the date key in the dictionary and how would I implement it here?

Thanks!

EDIT:

Found the answer about 5 seconds after posting this. The code I needed was:

NSSortDescriptor *aSortDescriptor = [[NSSortDescriptor alloc] initWithKey:@"date" ascending:YES];
[sortedFiles sortUsingDescriptors:[NSArray arrayWithObject:aSortDescriptor]];

So stupidly easy, I've spent all day on this!

Hope this helps someone!

Just to provide a more complete code for anyone looking for it:

NSFileManager * fm = [NSFileManager defaultManager];
NSArray * files = [fm contentsOfDirectoryAtURL:[NSURL URLWithString:@"/path/to/dir/"] includingPropertiesForKeys:[NSArray arrayWithObject:NSURLCreationDateKey] options:NSDirectoryEnumerationSkipsHiddenFiles error:nil];

if ((nil != files) && ([files count] > 0)){
    NSArray * sortedFileList = [files sortedArrayUsingComparator:^NSComparisonResult(id obj1, id obj2) {
        NSDate * mDate1 = nil;
        NSDate * mDate2 = nil;
        if ([(NSURL*)obj1 getResourceValue:&mDate1 forKey:NSURLCreationDateKey error:nil] &&
            [(NSURL*)obj2 getResourceValue:&mDate2 forKey:NSURLCreationDateKey error:nil]) {
            if ([mDate1 timeIntervalSince1970] < [mDate2 timeIntervalSince1970]) {
                return (NSComparisonResult)NSOrderedDescending;
            }else{
                return (NSComparisonResult)NSOrderedAscending;
            }
        }
        return (NSComparisonResult)NSOrderedSame; // there was an error in getting the value
    }];
}

There are other keys one can use instead of NSURLCreationDateKey -- full list is in "Common File System Resource Keys" section of NSURL Class Reference

Just to clarify, the answer was:

NSSortDescriptor *aSortDescriptor = [[NSSortDescriptor alloc] initWithKey:@"date" ascending:YES];
[sortedFiles sortUsingDescriptors:[NSArray arrayWithObject:aSortDescriptor]];