Getting document instance from NSPersistentDocument?

Question

I'm still fairly new to Objective C and programming in general, so if my question is inane please forgive me.
Here is what I'm stuck on. I'm currently working on an Cocoa desktop app that uses NSPersistentDocument. I currently have a view controller that manages a modal window. I would like to save to the ManagedObjectContext in one of that view controller's methods. According to Apple's documentation on Core Data"
"The context is in effect also your gateway to the rest of the Core Data infrastructure. As such, it is expected that you either keep a reference to the context, or you have a means of easily retrieving it—for example, if you are developing a document-based application that uses NSPersistentDocument, you can use the document class’s managedObjectContext method."
and elsewhere
"Where a managed object context comes from is entirely application-dependent. In a Cocoa document-based application using NSPersistentDocument, the persistent document typically creates the context, and gives you access to it through the managedObjectContext method."
and finally
"Getting a Managed Object Context
In OS X:
In an single-coordinator applications, you can get the application’s context directly from the application delegate.
In document-based applications, you can get the context directly from the document instance."
I think I'm missing the bigger picture here. My questions is... what is the document instance and how do I access it from other classes? This method in my modal view controller:
" - (IBAction)saveContext:id)sender {
if ([tagsArray count] != 0) {
    int objectcount;
    for (objectcount = 0; objectcount < [tagsArray count]; objectcount ++){
        Tag *singleTag = (Tag *) [NSEntityDescription insertNewObjectForEntityForName:@"Tag" inManagedObjectContext:self.managedObjectContext];
        singleTag.tagname = [tagsArray objectAtIndex:objectcount];
        singleTag.video = selectedFile;
        NSLog(@"Tagnames %@",singleTag.tagname);
[NSApp stopModalWithCode:NSOKButton];
[self.window close];
Gives me a "No known class method for selector 'managedObjectContext' compiler warning. Actually any method I try to call on the Document class gives the same warning. Something tells me the document instance is NOT called by "Document" because it's talking about a class method, but I have no clue what I should put in it's place. FWIW making an additional managedObjectContext in the view controller does not work as NSPersistentDocument does not allow more than one. I tried declaring "document" as a property in the view controller like this:
@property (strong) Document *docController;
But that's creating a new instance of the Document class rather than referencing the pre-existing one. The context is not getting saved because it's deallocated as soon as the window is closed. Obviously I'm thinking about this the wrong way. There isn't much info out there on core-data & document based apps. Can someone help me with this? I've been stuck on this for quite a while now and am desparate for help.
Thanks.

Answer 1

hi,
i think, that's not possible in that way you expect it.
the only idea, i have, is to use the jvmpi interface.
if you write your own profiler using jvmpi, your java program
will reach a c or c++ dll-function JVM_OnLoad().
There you have an instance of the java vm.
but still you are a thread of the vm.
How to pass it to a diffrent process ?
maybe via a variable which is shared by the dll with
another process.