Local storage & caching

Sometimes only relying on in-memory data is not enough. For example, you might want to persist fetched Podio content to disk across application launches.

All domain objects in PodioKit inherits from PKTModel. This class is conforms to the NSCoding protocol, meaning every subclass can be serialized, for example using NSKeyedArchiver/NSKeyedUnarchiver. Using PodioKit in your application, this gives you a lot of flexibility on how to persist these domain objects should you find the need.

For convenience, PodioKit provides a very simple key/value solution for storing objects conforming to NSCoding on disk with the PKTDatastore class.

Using PKTDatastore

PKTDatastore is a thread-safe, disk based key/value store. It can persist any object conforming to NSCoding and does so by simply archiving it to disk on a background thread. It also contains its own internal caching mechanism to avoid hitting the disk on every access. This internal cache will, on iOS only, be cleared if a low memory warning is issued.

To use PKTDatastore, you can either use the singleton instance or create your own store:

PKTDatastore *store = [PKTDatastore sharedStore];
// or...
PKTDatastore *store = [PKTDatastore storeWithName:@"MyStore"];

The latter will create a seperate location on disk where all objects will be stored. To store an object for a specific key, use the storeObject:forKey: method or subscripting:

NSArray *numbers = @[@1, @2, @3];

[[PKTDatastore sharedStore] storeObject:numbers forKey:@"MyNumbers"];
// or...
[PKTDatastore sharedStore][@"MyNumbers"] = numbers;

To retrieve an object from the store, you can use either the synchronous storedObjectForKey: or the asynchronous fetchStoredObjectForKey:. We encourage using the latter to keep your application responsive and istead register a completion handler on the PKTAsyncTask returned from the method:

NSArray *numbers = [[PKTDatastore sharedStore] storedObjectForKey:@"MyNumbers"];

// or...

[[PKTDatastore sharedStore] fetchStoredObjectForKey:@"MyNumbers"] onComplete:^(NSArray *numbers, NSError *error) ^{
  // Use the numbers...
}];