Quirks with doing simple task of creating object and then using on main thread as soon as possible

[Shuab]

Either need to make an easier way to do this and/or a related example in the README or the example project. And my first solution of re-querying the object by ID is both inefficient and getting away from the design goals of the framework, I think.

The code from your comment in #1 was the first thing I had tried when I ran into it:

Cd.transact {
    let obj = try! Cd.create(MyObj.self)
    obj.prop = 3
    try! Cd.commit()
    dispatch_async(dispatch_get_main_queue()) {
        let myMainThreadObj = Cd.useInCurrentContext(obj)!
        // Do something with object
    }
}

But I run into this inside of useInCurrentContext():

        guard let originalContext = object.managedObjectContext else {
            Cd.raise("You cannot transfer an object without a existing context.  This object may be transient, or it's original context has been destroyed.")
        }

I assume because the temporary context for the transaction is gone and so the object has no MOC.

I got it to work using a synchronous dispatch to main - what do you think about potentially keeping that temporary context for the transaction around in the case of heavy-ish work done in the synchronous code on main? If that doesn't seem bad, then I think that's the best route to go. My first concern was with stuff like a race condition with the restoring of existingContext and existingNoCommit, but I guess those are protected because that thread is blocked until the newWriteContext.preformBlockAndWait is done. This is what I'm using now:

Cd.transact {
    let obj = try! Cd.create(MyObj.self)
    obj.prop = 3
    try! Cd.commit()
    dispatch_sync(dispatch_get_main_queue()) { // <-- SYNCHRONOUS
        let myMainThreadObj = Cd.useInCurrentContext(obj)!
        // Do something with object
    }
}

[jmfieldman]

I think I might be too heavy-handed with the guard against transferring w/o an existing context. If the NSManagedObject has a permanent objectID I should let it pass as well. I think this would make the async version work, but will test later.

In fact, I should probably be checking against temporary IDs, but I think the check on originalContext.hasChanges is doing that implicitly (since any context w/ an object that isn't saved will have changes..)

[jmfieldman]

Ok, 0.11.1 is up with the change to context-checking on useInCurrentContext. Now any object with a persistent ID should be useable; still relying on the hasChanges flag to catch transient objects though.

Also added some more content to the readme about this, as well as notes on the update handler.

[jmfieldman]

(btw, added code to the basic example's handleAdd function to show the object being dispatched and having an updateHandler assigned to it)

[Shuab]

Great, looks good!