Recurring background task in iOS

Question

I would like to make an app that periodically, sporadically and automatically downloads some data from a list of user-defined sites, so it can then analyze and show historical graphs and other reports based on that data.

If I were to do this in Windows, I'd use the system Task Scheduler; if I were in Unix, I'd use cron; if I were in Android I'd use services. I would like to know how to do it in iOS.

As far as my research goes, this is not trivial in iOS, as there is no public interface for doing this. There are however, some workarounds to get this done:

• Pull the historical data when the app awakens: Not possible, because I am not the provider of the data, and most of the data providers I will support don't store or offer access to historical data.

• Download the data myself and have the clients pull it when awakening: Not desirable. Not only this requires additional costly infrastructure on my side (which would mean charging my users for what I intend to be a free app), but also some of the content providers require login credentials. I'd rather not ask for my users' login information to access information they can get themselves.

• Save a timestamp from the last update and download data when the user puts the app in the foreground if the timestamp is expired: This doesn't serve my purposes, because data may (and is expected to) rapidly change in time. The entire purpose of this app is to automatically download this data periodically so all the historical data is available once the user opens the app again.

• Use local notifications: It's pretty much the same as before. It requires user interaction to start the app, and the entire point of the app is to get this data even when the user is not using the device.

• Use push notifications: Since these are just notifications that require user interaction to awaken the app, they can't be used for the same reason as local notifications. It seems you can process all pending push notifications once the app awakens, but I read you can't define custom fields for these notifications though.

• Use background tasks: This technically seems the most promising of all options, but this is only available for very specific types of apps. I guess that a "Newsstand app" is the closest I can get, and it is actually meant to download data in the background. However, as it is named, it is meant for downloading "magazine or newspaper issues". Whether what I want to do can be classified as this is completely up to the app reviewer, and I'd rather not make an app that may get rejected on a technicality.

So, my question is: are there any other ways to do this that I am not aware of? Are there any apps that already do something similar?

Answer 1

I think you have one further option, location based updates, but this depends on your users moving around regularly.

See e.g. http://blog.instapaper.com/post/24293729146 and http://blog.news.me/post/21643399885/introducing-paper-boy-automatically-download-your-news

Answer 2

Your only choice in iOS really is to go with server-side infrastructure. Don't be afraid of charging the user; if the service you're providing is really useful, people will pay. I do get that it's a lot of extra work, etc, but it really is the only way.

Newsstand apps can only download data once a day, and they still require s server-side push notification to start the download, so you would have to put some infrastructure in place. More importantly, though, Apple is actually quite strict about being in the newsstand; I've been thru this a few times: you don't necessarily have to be a magazine/periodical, but your app should be primarily used for content distribution.

Answer 3

Your assessment is correct. Your only 2 options are to host your own service that periodically downloads the data (your second bullet point) or use Newstand. For Newstand, it's possible that your app could fit the definition; it may just depend on how you characterize the app.