ImageSync

ImageSync is an Objective-C/iOS library I developed to facilitate the synchronization of images based on a database timestamp. ImageSync compares the device's local image timestamps (stored in a property list) with those of the remote server and downloads any new/updated images asynchronously. After all images are downloaded, ImageSync updates the image timestamp record for future synchronization.

Eventually I hope to encapsulate the dispatching of asynchronous threads in the ImageSync library, as opposed to having the user/developer write this code. However, in its current state, the code gives the developer granular control over multi-threading functionality.

Example

- (void)syncIcons {
    TMImageSync *sharedSync = [TMImageSync sharedSync];
    sharedSync.remoteURL = [NSURL URLWithString:[NSString stringWithFormat:@"%@%@", SERVER_URL, IMAGE_CONTROLLER_PATH]];
    sharedSync.imagePlistName = IMAGE_PLIST_FILENAME;
    
    // Set up asynchronous dispatch group
    dispatch_queue_t queue = dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0);
    dispatch_group_t group = dispatch_group_create();
    
    for (CAContactCategory *cc in self.fetchedResultsController.fetchedObjects) {
        //NSLog(@"cc.icon: %@", cc.icon);
        if (![cc.icon isEqualToString:@""]) {
            // Add a task to the group
            dispatch_group_async(group, queue, ^{
               [sharedSync syncImage:cc.icon withTimestamp:cc.modified]; // As of now, just checking to see if parent was modified
            });
        }
    }
    
    // Cannot make any more forward progress until threads finish
    // wait on the group to block the current thread.
    dispatch_group_wait(group, DISPATCH_TIME_FOREVER);
    
    // Update image timestamp record (plist)
    if (sharedSync.newImageTimestampsExist) {
        [sharedSync writeImageTimestamps];
    }
}