Coredata performBlock then return the new value

Question

How to return the new object saved in coredata if I am using performBlock to save a managedObjectContext?

The requirement is, add an entry in coredata,

Answer 1

Rather than return the newly created Core Data object, pass the constructor method a block with a parameter of the type of object you're creating.

When the object has been created within the Managed Object Context's performBlock: block, call your completion block and pass in the newly constructed Core Data object.

+ (void)coreDataObjectWithJSON:(NSDictionary *)json completion:(void (^)(NSYourCoreDataObject *coreDataObject))completion {

    [yourManagedObjectContext performBlock:^{

        NSEntityDescription *entity = [NSEntityDescription entityForName:... inManagedObjectContext:...];

        NSYourCoreDataObject *coreDataObject = [[NSYourCoreDataObject alloc] initWithEntity:entity insertIntoManagedObjectContext:...];

        if (completion) {
            // "return" the new managed object
            completion(coreDataObject);
        }
    }];
}

Answer 2

I did some research and found that was not too difficult to fix this issue:

I replaced performBlock with performBlockAndWait and it worked.

Reason is straightforward: performBlock is asynchronous, while performBlockAndWait is synchronous.