Swift - Save huge array of strings with UserDefaults

Question

I have a social app, where the user can like photos... So, in order not to wait for fetching the data from the server, I want to store to the device, an array of strings, containing the photos' objectIds.. The question is, considering the user can like thousands of photos, is it good practise to use UserDefaults to achieve that?

Answer 1

EDIT As pointed out by Eric Aya in the comments, NSUserDefaults aren't loaded automatically into memory when the app launches.

NSUserDefaults are loaded into memory when your application launches If you have a particularly large amount of data stored in NSUserDefaults then the time it takes your app to launch to load NSUserDefaults will be impacted by the amount of IO required to retrieve your data. The intended use case for NSUserDefaults is to store small sets of data such as default user settings.

A Plist may be a better solution (NSUserDefaults is just a Plist, the difference being is it's loaded automatically for you when the app launches). You will still have the same issues with load times when you decide to grab the Plist as you will be loading a file (the Plist) into memory. You will be able to handle this with something like a progress bar or an activity indicator which gives the user a nicer experience. than having to wait longer than usual for an app to open. CoreData is another option (usually intended for more complex data structures than strings, on the flip side it gives you the capability to scale your storage needs very easily if the complexity of your data increases), there's a fairly steep learning curve involved but it's a wonderful feature and is well documented by Apple: https://developer.apple.com/library/content/documentation/Cocoa/Conceptual/CoreData/

I would also recommend storing the data on a server where you could expose it via an API and cache the response using a Plist/CoreData/Whatever you like. This way if your users change devices they will still have access to the same data as it's stored remotely.

Good luck!