Use a single background context.

Package.resolved

@@ -6,7 +6,7 @@
  "repositoryURL": "https://github.com/jaredsinclair/etcetera.git",
  "state": {
  "branch": "spm",
- "revision": "88b6533ddce800ef46cb07e8db5fc18d804f8c96",
+ "revision": "4ec9ca6978c4156980c706a2b908c32e917a1950",
  "version": null
  }
  }

Sources/FuckShitStack/FuckShitStack.swift

@@ -43,6 +43,18 @@ public class FuckShitStack {
 
  private let container: NSPersistentContainer
  private let backgroundQueue: OperationQueue
+ private var _backgroundContext = Protected<NSManagedObjectContext?>(nil)
+
+ private var backgroundContext: NSManagedObjectContext {
+ assert(backgroundQueue.isCurrent)
+ return _backgroundContext.access { context -> NSManagedObjectContext in
+ if context == nil {
+ context = container.newBackgroundContext()
+ context!.mergePolicy = NSMergeByPropertyObjectTrumpMergePolicy
+ }
+ return context!
+ }
+ }
 
  // MARK: Factory / Init
 
@@ -132,6 +144,8 @@ public class FuckShitStack {
  if let error = error {
  handler(.failure(error))
  } else {
+ container.viewContext.mergePolicy = NSMergeByPropertyStoreTrumpMergePolicy
+ container.viewContext.automaticallyMergesChangesFromParent = true
  let stack = FuckShitStack(container: container)
  handler(.success(stack))
  }
@@ -207,7 +221,7 @@ public class FuckShitStack {
  let task = BackgroundTask.start()
  let op = BlockOperation { [weak self] in
  guard let this = self else { return }
- let context = this.container.newBackgroundContext()
+ let context = this.backgroundContext
  context.performAndWait {
  block(context)
  if saveAfterward {
@@ -227,8 +241,8 @@ public class FuckShitStack {
  public func sync_performInBackground(_ block: @escaping (NSManagedObjectContext) -> Void) {
  let op = BlockOperation { [weak self] in
  guard let this = self else { return }
- let context = this.container.newBackgroundContext()
- context.performAndWait {
+ let context = this.backgroundContext
+ this.backgroundContext.performAndWait {
  block(context)
  }
  }