CODEWITHSUNDEEP
ioscocoa-touchcore-dataasynchronousnsfetchedresultscontroller
user984694
user984694

Reputation:

Dealing with asynchronous download delays before displaying data

My app connects to a Parse server asynchronously and downloads the necessary data into the app's Core Data store . I would then like to display this data in a tableview. But in most cases -- as the connection is asynchronous -- the table view can access the data store much faster than the downloaded does . In this situation, I get an empty table view cell, and just after that the data is ready in the data store.

What is the best way to deal with the delays caused by asynchronous downloads? Is there a concept that I'm missing? Is it NSFetchedResultsController?

Upvotes: 1

Views: 139

Answers (2)

Marcus S. Zarra
Marcus S. Zarra

Reputation: 46718

Asynchronous is a design problem that you will need to work with. Look to some of the other popular applications in your field and see how they solve it. Do they show a spinner (I personally hate that) or do they show some unobtrusive indicator that data is being downloaded (better)?

If you use a NSFetchedResultsController (which I am guessing by your question you are not currently) you will get the data displayed once it is saved in Core Data with no additional effort on your part. So you can at least show the data as soon as possible.

In the meantime, I recommend let the cells/table be empty and let the user know that your app is working. Display the data as soon as possible. Perhaps consider downloading the data in pieces so that they can start to see it asap.

Upvotes: 1

Lorenzo B
Lorenzo B

Reputation: 33428

What do you think is the best way to deal with the delays caused by asynchronous downloads?

It depends on requirements you have. In particular, if the user can interact with UI during async downloads, you can do nothing on it, otherwise you could use just a spinner to alert him something is downloading and stop the interaction until the sync as finished.

Anyway, in both cases, you should say something about the download. In particular, are you saving data in a different thread (different from the main one)? If so you should merge the changes from the context you use in background to the context associated with the NSFetchedResultsController (always the main one since NSFetchedResultsController manages UI elements).

Is there a "concept" that I miss and is it NSFetchedResultsController?

Did you setup correctly the delegate NSFetchedResultsControllerDelegate? If so, the NSFetchedResultsController tracks changes on the entity you registered on your fetch request. Not changes will happen for other entities.

Upvotes: 1

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