why am I getting an "unknown type name NSManagedObjectContext" in this code?

Question

any ideas why am I getting an "unknown type name NSManagedObjectContext" in this code?

I'm basically adding core data to an existing project. I've added the coredata lines + I have added in the CoreData.framework to the project. To do this I went:

• when to application target
• build phases
• link binary with library
• then added the CoreData framwork
• then dragged it down on the project navigator so it appeared with the other framework icons in Xcode

Note sure what else I have to do? The CoreDataBooks example code that looks pretty much the same as what I have seems to compile

#import <UIKit/UIKit.h>

@interface myAppAppDelegate : NSObject <UIApplicationDelegate> {
    UIWindow *window;
    UINavigationController *navigationController;
}

@property (nonatomic, retain) IBOutlet UIWindow *window;
@property (nonatomic, retain) IBOutlet UINavigationController *navigationController;

// Core Data
@property (nonatomic, retain, readonly) NSManagedObjectContext *managedObjectContext;  // ERROR: unknown type
@property (nonatomic, retain, readonly) NSManagedObjectModel *managedObjectModel;   // ERROR: unknown type
@property (nonatomic, retain, readonly) NSPersistentStoreCoordinator *persistentStoreCoordinator;   // ERROR: unknown type

- (void)saveContext;
- (NSURL *)applicationDocumentsDirectory;

@end

Solution 1

You then have to import the Core Data framework headers into any files that use Core Data classes.

#import <UIKit/UIKit.h>
#import <CoreData/CoreData.h>

Solution 2

As Greg said above, the way XCode 4 handles this is by adding #import <CoreData/CoreData.h> into the [projectname]_Prefix.pch file which I found in Other Sources folder/group.

Comments

[Greg]

oh - I went back to the template that XCode 4 creates for a CoreData window based iPhone app and see, whilst there is no import like you suggest, there is this "#ifdef OBJC" section in a project-Prefix.pch file that does have the CoreData import statement in it

[joshaidan]

Putting the declaration in the project-Prefix.pch file as Greg mentioned, I think is the better approach.

[edzio27]

Remember also to add CoreData framework in project Build Phases.

[jheriko]

-1 This is worst practice. include headers only where you need them, not everywhere. its a shame that apple provide this prefix header out of the box. the correct use for it is to improve compile times... not to hide dependencies.