ID declaration error when adding Core Data to an existing Xcode project

Question

I have an existing project and I want to use CoreData.

After creating the project, CoreData.framework has already been added to my Frameworks group, and it is under Link Binary With Libraries in my Target → Build Phases project. I did not check “Use basic data” when I created this project - the checkbox was even there - it was just in my project. I am using Xcode version 4.6.3.

Reading the tutorials, I went to my App-Prefix.pch and added import to CoreData. Now it looks like this:

 #import <Availability.h> #ifndef __IPHONE_5_0 #warning "This project uses features only available in iOS SDK 5.0 and later." #endif #ifdef __OBJC__ #import <UIKit/UIKit.h> #import <CoreData/CoreData.h> #import <Foundation/Foundation.h> #endif 

Then I added the following to AppDelegate.h :

 @property (readonly, nonatomic, strong) NSManagedObjectContext *managedObjectContext; @property (readonly, nonatomic, strong) NSManagedObjectModel *managedObjectModel; @property (readonly, nonatomic, strong) NSPersistentStoreCoordinator *persistentStoreCoordinator; - (void)saveContext; 

And now, when I override getter for managedObjectContext , Xcode throws an error:

Using the undeclared identifier "_managedObjectContext"; did you mean 'NSManagedObjectContext'?

This is my getter method in AppDelegate.m :

 - (NSManagedObjectContext *)managedObjectContext { if(_managedObjectContext != nil) return _managedObjectContext; NSPersistentStoreCoordinator* psc = [self persistentStoreCoordinator]; if(psc != nil) { _managedObjectContext = [[NSManagedObjectContext alloc] init]; [_managedObjectContext setPersistentStoreCoordinator:psc]; } return _managedObjectContext; } 

I also tried putting the .pch file in my resources to copy the bundle, but to no avail. Help?

Answer 1

You configured everything correctly (note that you do not need to add PCH to the build phase of copy resources). The reason you get this error is because _managedObjectContext ivar is not synthesized because you override getter on a read-only property. You need to either change the property so that it is readwrite (which I would not recommend), override the property as readwrite in the class extension, or define ivar manually in the class extension or implementation block.

Answer 2

For readonly properties that you even implement, there is no Ivar created by the compiler. Declare a variable

NsmanagedObjectContext * _managedObjectContext;