Core Data Utility Tutorial - Sample Code

Question

I am following apples Core Data Utility tutorial from http://developer.apple.com/mac/library/documentation/Cocoa/Conceptual/CoreDataUtilityTutorial/Articles/00_introduction.html

I have only just started it and have already encountered an error (more than likely my error, not anyone else's).

Given the code

#import <Foundation/Foundation.h>
#import <CoreData/CoreData.h>
#import <objc/objc-auto.h>

NSManagedObjectModel *managedObjectModel();


int main (int argc, const char * argv[]) {
    objc_startCollectorThread();

    return 0;
}

NSManagedObjectModel *managedObjectModel() {

    static NSManagedObjectModel *mom = nil;
    if(mom != nil){
        return mom;
    }
    mom = [[NSManagedObjectModel alloc] init];
    // implimentation continues
    return mom;
}

I get the error:

"_OBJC_CLASS_$_NSManagedObjectModel", referenced from: objc-class-ref-to-NSManagedObjectModel in CoreDataUtility.o

I am guessing that the issue is caused by my forward declaration of the managedObjectModel() function, but I cannot solve as to why I am getting the issue I am.

Answer 1

The forward decleration looks all right. It matches that provided by Apple.

Most likely, the error is caused because the Core Data Framework is not added to the project.