Question

I have created a small test app. It creates a new company and a number of x employees.

The employees are created in their own thread and as soon as that’s done, they will be added to a company.

Because it’s not allowed to share managed objects between threads, I use the company’s object id.

In order not to read/write the same managed object context at the same time, I create a temporary context for each thread. I use – (void)mergeChanges:(NSNotification *)Notifikation and merge the changes between the man context and the context from the thread.

I display both the company and its employees in two table views using two app controllers and bindings.

But there is still a bug I can’t fix. Everytime I create a new company with employees, not all employees appear in the table view. Somehow they get lost, but I can’t figure out where.

I have uploaded the Xcode project here: http://uploading.com/files/7894m9mc/CoreDataMultiThreading.zip/

I am trying to find the bug for one week now 🙁 Maybe someone else has more luck.

Note: What I want to try with that app is to create many objects in their own thread (employees) and add these objects to one and the same object (company) as soon as they are created.

( please excuse my bad pronunciation )

Answer 1

The problem is arising because many of the Employee objects have their company relationship set to nil after the merge with the foreground thread. Since they have no company relationship object, they don’t show up in the UI.

I’m not sure why the merge is setting the relationship to nil. It might have something to do with having multiple merges occurring at the same time or with trying to merge unfaulted fault objects.