OBJECTIVE-C Self-study Note (3)-use of data sets

Hit by the example on the book:

#import <Foundation / Foundation.h>
int main (int argc, const char * argv []) {
    @autoreleasepool {
        // Declaration of file management objects
        NSFileManager * manager;
        // Create NSFileManager initialization by defaultManager method
        manager = [NSFileManager defaultManager];
        // Declaration to traverse the path
        NSString * home;
        // Initialize the directories to be traversed: user root directory
        home = [@ "~" stringByExpandingTildeInPath];
        // Declaration file traversal object
        NSDirectoryEnumerator * direnum;
        // Initialize the file traversal object, and use the file directory object home as a parameter
        direnum = [manager enumeratorAtPath: home];
        // variable list to save traversed files
        NSMutableArray * files;
        // The initial size is set to 42
        files = [NSMutableArray arrayWithCapacity: 42];
        // enumerate the iterated objects
        NSString * filename;
        // Use the iterative method to iterate through all the elements in the enumeration one by one
        while (filename = [direnum nextObject]) {
            // Determine if the file is a jpg file
            if ([[filename pathExtension] isEqualTo: @ "jpg"]) {
                // Add the file name to the list
                [files addObject: filename];
            }
        }
        // Declaration file list enumeration
        NSEnumerator * fileenum;
        // Initialize the enumeration object
        fileenum = [files objectEnumerator];
        // enumerate through all elements
        while (filename = [fileenum nextObject]) {
            // Print information
            NSLog (@ "% @", filename);
        }
    }; // autoreleasepool
    return 0;
} // main

Output

2015-01-27 23: 00: 11.181 04.01 Shapes-Inheritance [449: 9009] Desktop / psb.jpg
2015-01-27 23: 00: 11.194 04.01 Shapes-Inheritance [449: 9009] Documents / aodci / Player Information / QPR / 15.jpg
2015-01-27 23: 00: 11.194 04.01 Shapes-Inheritance [449: 9009] Documents / aodci / Player Information / QPR / 19.jpg
2015-01-27 23: 00: 11.194 04.01 Shapes-Inheritance [449: 9009] Documents / aodci / Player Information / QPR / 22.jpg
2015-01-27 23: 00: 11.195 04.01 Shapes-Inheritance [449: 9009] Documents / aodci / Player Information / QPR / 24.jpg
2015-01-27 23: 00: 11.195 04.01 Shapes-Inheritance [449: 9009] Documents / aodci / Player Information / QPR / 4.jpg
2015-01-27 23: 00: 11.195 04.01 Shapes-Inheritance [449: 9009] Documents / aodci / Player Information / QPR / QPR.numbers / preview-micro.jpg
2015-01-27 23: 00: 11.195 04.01 Shapes-Inheritance [449: 9009] Documents / aodci / Player Information / QPR / QPR.numbers / preview-web.jpg
2015-01-27 23: 00: 11.196 04.01 Shapes-Inheritance [449: 9009] Documents / aodci / Player Information / QPR / QPR.numbers / preview.jpg
2015-01-27 23: 00: 11.196 04.01 Shapes-Inheritance [449: 9009] Documents / aodci / Player Information / Burnley / 11.jpg
2015-01-27 23: 00: 11.196 04.01 Shapes-Inheritance [449: 9009] Documents / aodci / Player Information / Burnley / 21.jpg
2015-01-27 23: 00: 11.196 04.01 Shapes-Inheritance [449: 9009] Documents / aodci / Player Information / Burnley / 7.jpg
2015-01-27 23: 00: 11.215 04.01 Shapes-Inheritance [449: 9009] Documents / aodci / Player Information / Burnley / Burnley.numbers / preview-micro.jpg
2015-01-27 23: 00: 11.215 04.01 Shapes-Inheritance [449: 9009] Documents / aodci / Player Information / Burnley / Burnley.numbers / preview-web.jpg
2015-01-27 23: 00: 11.215 04.01 Shapes-Inheritance [449: 9009] Documents / aodci / Player Information / Burnley / Burnley.numbers / preview.jpg
2015-01-27 23: 00: 11.216 04.01 Shapes-Inheritance [449: 9009] Documents / aodci / Player Information / Chelsea / 10.jpg
2015-01-27 23: 00: 11.216 04.01 Shapes-Inheritance [449: 9009] Documents / aodci / Player Information / Chelsea / 14.jpg
2015-01-27 23: 00: 11.216 04.01 Shapes-Inheritance [449: 9009] Documents / aodci / Player Information / Chelsea / 19.jpg
2015-01-27 23: 00: 11.217 04.01 Shapes-Inheritance [449: 9009] Documents / aodci / Player Information / Chelsea / 2.jpg
2015-01-27 23: 00: 11.217 04.01 Shapes-Inheritance [449: 9009] Documents / aodci / Player Information / Chelsea / 21.jpg
2015-01-27 23: 00: 11.217 04.01 Shapes-Inheritance [449: 9009] Documents / aodci / Player Information / Chelsea / 4.jpg
2015-01-27 23: 00: 11.218 04.01 Shapes-Inheritance [449: 9009] Documents / aodci / Player Information / Chelsea / 7.jpg
2015-01-27 23: 00: 11.218 04.01 Shapes-Inheritance [449: 9009] Documents / aodci / Player Information / Chelsea / chelsea.numbers / preview-micro.jpg