Managed Object Context in Tab Bar View

Question

Ok. this one's a challenge.

I have a tableview within a navigation controller.

I push it from the root, where I have an add action that allows me to add a new record. That works fine.

Now what I've tried to do is add this tableview to a tab bar view (without a tab bar controller cuz that won't work) but within the same navigation controller.

So what I want to do is this: Root > TabBarView (loads Tableview) > add new record.

The problem lies in the managed object context, I get the whole "can't find entity error" but I have no idea how to fix it.

I've managed to get the AddRecord modal view controller to show up from the tabBarView, but it presents itself without a navigationbar, whereas if I try to add a record in the solitary tableView (outside of the tabbar) its no problem.

I'm now calling my methods from the TabBarView's navigationBarbuttons, routing through to the tableviews methods.

I know my methods have to be called from the tabBarView instead of the actual tableview now, and they do fire, but I don't know how to manage the MOC when its in a tabView.

Oh, and this is based on coredata recipes and books, so when the add record method is fired, it creates a new MOC to create it, then reintegrates back in the main MOC when you're done.

Any ideas?

Answer 1

It sounds like you have a couple of problems.

1. "Can't find entity" error -- this depends on which Managed Object Context you're using. If you created a separate MOC to manage the object you're editing (which is a good idea, by the way), make sure you assign it a Persistent Store Coordinator. This is how an MOC discovers what objects are available. If you're using the MOC created in the App Delegate, make sure you're spelling the name of the entity correctly.
2. No Navigation Bar in sheet -- When you push a view controller onto a navigation controller, its navigationItem is used to populate the navigation bar. When you present a view controller as a sheet, only the view controller is displayed. It is not embedded in a navigation controller. In order to get the navigation item to display, you'll need to create a new navigation controller with your view controller as the root, and then present the navigation controller's view.

Answer 2

As far as the main MOC goes, views and controllers should be irrelevant. Obtain a reference to the MOC in whatever controller you are using and operate with that MOC. If your application delegate creates the main MOC, make it a property of that delegate and access that from your view or tab controller.

I don't quite follow what navigation problem you're having, but if there's no navigation bar when you need one, I suspect you need to create and add a UINavigationController somewhere that you're adding a UIViewController subclass. Make the subclass the root of the new UINavigationController and put the controller into the tab or whatever.

Your managed object context (MOC) should not be dependent on navigation or views. It's part of the model. (Although as you know, a 2nd MOC for a cancelable edit view would be dependent on navigation to the extent that you create it for use by the editor.)