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Editorial Team
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Asked: 2026-06-06T04:31:08+00:00

I currently have an iPhone project with a tab bar. On the tabbar there

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I currently have an iPhone project with a tab bar. On the tabbar there are two views. Both of the views load or save data to a Core Data database (Both of these view initiate a method that collects data from a webservice and saves it in a database). When the view is loaded, it loads data from the database that populates a table in the view. If I run the app and click on the second view in the tabbar, the first view is still loading data from a webservice and inserting it into a database on a seperate thread. This is fine but once the first view has finished loading all the data into the database from the webservice, it freezes both view controllers ONLY if the second view controller is loading data from the database.

There is no error to the console and no indication by xcode that there is any error. All my processes work on different threads so there is not issue with the main thread freezing. The pulling data from a webservice and saving it to the database is a method and at the end of the method I have put NSLog(@"View Controller 1 Save Complete"). As soon as this is called AND the second view controller is still loading data, it freezes. The entire app is unresponsive (Nothing works).

I have looked through info on other SO questions and it recommended that I declare a new NSManagedObjectContext every fetch or insert and I have done that but it has not solved the problem.

If anyone knows what is happening or you want to know some more info, please let me know.

EDIT:
I am using Xcode 4.5 and IOS 6 simulator. This is the beta verion of the new IOS that was released a week ago. I know that this is not the error though as I had this problem before I started using the beta versions.

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1 Answer

  1. Editorial Team

    A possibility that I have run into in the past, is trying to interact with an MOC on a thread which is different than the one it was created on. This kind of thing can happen if you are trying to do concurrency, and you must be very careful to know which thread you are on at all times when talking to an MOC. For example, with asynchronous things, your callbacks might be executing on a different thread than you think (i.e. viewDidLoad happens on the main thread, so if you are creating an MOC there, you cannot use it from a different thread later).

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