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I have an NSManagedObjectContext, i make a couple of changes to the model and then... to "commit" the transactions, what's the difference between doing:
[context save:&error];
and
[context processPendingChanges];
It seems they both do the same thing.
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When one of the managed object contexts is saved, its changes are pushed through the persistent store coordinator to the persistent store.
Core Data is designed to work in a multithreaded environment. However, not every object under the Core Data framework is thread safe. To use Core Data in a multithreaded environment, ensure that: Managed object contexts are bound to the thread (queue) that they are associated with upon initialization.
In a nutshell, processPendingChanges changes the state of the current object graph. save will save the current object graph to disk.
Calling save will call processPendingChanges automatically.
If you think of a text file in a word processor, save is analogous to saving the document to disk.
processPendingChanges is analogous to telling the word processor to update it's internal state of the document after an edit, but without saving to disk. This usually triggers updates to the UI such as updating a displayed word or line count, doing any necessary formatting, etc...
In my experience, for the iPhone, you rarely need processPendingChanges. I believe it is mostly intended for Mac OS X and handling advanced or complicated undo management or updating UI bindings.
For the iPhone, this is usually done to trigger NSFetchedResultsControllers to update table views. Even then, this is somewhat rare. If you aren't sure just stick with save
For more info, go study the difference between NSManagedObjectContextDidSaveNotification and NSManagedObjectContextObjectsDidChangeNotification in the docs.
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