NSManagedObject's managedObjectContext property is nil
core-data, iphone, nsmanagedobjectcontext
Solution
I recently ran into the same problem again, although it was in a different situation. I needed a temporary managed object context, completely separate from the main one, but I again ran into the problem of it disappearing after it goes out of scope. This time I decided to investigate further, and I ultimately realized that `managedObjectContext` is not a property of `NSManagedObject`, but a method. This means one of two things:
- If it uses a property in the underlying implementation, that property will not hold a strong reference to the context
- If the managed object context is derived in some other way, it will also not hold a strong reference to that context.
In either case, the context has no strong references, goes out of scope, and the `NSManagedObject`s have a `nil` `managedObjectContext`.
The solution was to simply keep the context around by creating a strong property for it.
Problem
I'm trying to create a temporary managed object context, and after a few screens of the user putting in information, I merge that context with the main context (to ensure that there are no "incomplete" objects are inserted). This is how I create my temporary context and how I insert an object in it: ``` if (!self.someManagedObject) { NSManagedObjectModel *model = [NSManagedObjectModel mergedModelFromBundles:@[[NSBundle mainBundle]]]; NSPersistentStoreCoordinator *storeCoordinator = [[NSPersistentStoreCoordinator alloc] initWithManagedObjectModel:model]; [storeCoordinator addPersistentStoreWithType:NSInMemoryStoreType configuration:nil URL:nil options:nil error:nil]; NSManagedObjectContext *managedObjectContext = [[NSManagedObjectContext alloc] init]; [managedObjectContext setPersistentStoreCoordinator:storeCoordinator]; self.someManagedObject = [NSEntityDescription insertNewObjectForEntityForName:@"SomeObject" inManagedObjectContext:managedObjectContext]; NSLog(@"%@", self.someManagedObject.managedObjectContext); } ``` This is a part of`viewDidLoad`. In the console it shows that managed object context has a value. However, right after this if statement (even within `viewDidLoad`, `self.someManagedObject.managedObjectContext` is nil. I can see why the local variable would not be available anymore (it simply goes out of scope), but the managed object's property should still be set, right? I know I can create a property to store the managed object context, but I'd rather get it to work this way.