Example background execution code for the blog post "Flapjack" on O'Reilly's engineering blog.

PerformInBackground.swift

dataAccess.performInBackground { [weak self] context in
    let pancake = context.create(Pancake.self, attributes: ["flavor": flavor, "radius": radius, "height": height])
    let error = context.persist()
    DispatchQueue.main.async {
        guard let self = self else { return }
        let foregroundPancake = self.dataAccess.mainContext.object(ofType: Pancake.self, objectID: pancake.objectID)
        completion(foregroundPancake, error)
    }
}