How do I create a global UIManagedDocument instance per document-on-disk shared by my whole application using blocks?

Question

I am trying to design a helper method which will retrieve a UIManagedDocument, then open and return it, so that I may access the same UIManagedDocument from several places i

Answer 1

You can execute the block with completionBlock(doc).

    [doc openWithCompletionHandler:^(BOOL success) 
     {
         // Can I call the completionBlock from above in here?
         // How do I pass back the opened UIDocument
        completionBlock(doc);
     }];

Let's assume that you have the following method implemented in the class that will be calling your openVacation method:

-(void)vacationOpened:(UIManagedDocument *)vacation
{
    NSLog(@"My Vacation: %@", vacation.description);
}

A sample line of code that would call your openVacation method would be:

[MyVacationsHelper openVacation:@"MyVacation1" usingBlock:^(UIManagedDocument *vacation){
    [self vacationOpened:vacation];
}];

The (UIManagedDocument *vacation) after the caret means that when you execute the block using the parentheses notation -- as in completionBlock(doc) --, you need to list a (UIManagedDocument *) as a parameter. The value of that parameter will be referred to as vacation inside the specified block. What I did in my block code sample above was call a method in my current class (self) and pass the parameter along to that method so that I could use it as needed (I just did an NSLog here to make sure that it worked).

Answer 2

I found a pretty helpful article - "Core Data with a Single Shared UIManagedDocument"