Core Data Background Context vs Main Context

Question

Created Jul ’20

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Hi,

I'm working on an app where I'm using Core Data to store some information on persistent storage. I'm having issues understanding and deciding how to deal with read/write operations.

At the moment, I have a QuoteGroupStorageManager class that wraps most of the operations in easy to use functions. You can see it below.

You can see that I'm fetching on the main context, and editing/deleting/inserting (apart from the addQuoteToGroup which I do on the mainContext because I use relationships, and the quoteGroup belongs on the mainContext - otherwise I get an error with illegal... object belongs to a diff context).

My question is, am I doing things right, in terms of performance? I'm using SwiftUI for the UI and when I delete a QuoteGroup for example, the UI is freezing for a while, until I make a new deletion. I'm wondering if it's because of the mixture of backgroundContext and mainContext. Which one should I use?

QuoteGroupStorageManager.swift

Thanks!

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Answer 1

lewis42 OP

Jul ’20

I would recommend using the viewContext for everything by default.

If you hit a real life scenario where this is causing an issue I would investigate how to solve that issue at that point, but it’s better to avoid complexity until you need it.

(To be clear I think this is a good question and this is not an intuitive answer. I think the contexts could be better labelled as “default” and “expert” or something like that)

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