- image name now has the LB prefix + hash value + UTC value.
- image fetcher removed the save child method from its implementation to avoid saving many times.
- LBCache singleton now has a child context, the child + parent save occurs when the app will resign active.
- LBCache singleton now has the updateDatabase method which is called only once when the app starts, it looks through all Images objects and remove the objects where no file is found at the path for imageURL, that means the OS removed them from caches directory and the object is no longer useful.
- the imageView subclass uses the childContext's (from the LBCache singleton.) performBlock method so the fetch or download will happen on a background queue.
- the imageView subclass checks if the file exists at the localURL, if not it download it again async.
define pragma directives.