OS X: Bindings, KVC, and KVO - Core Data - page 142

NSTableView , like NSOutlineView (as discussed in NSOutlineView , on page 148 ), plays
very nicely with Core Data. This is especially true when the NSTableView is
backed by an NSArrayController that is feeding the data. It is possible to use
NSTableView with a custom data source, if that is appropriate for the problem
at hand. However, when bound with an NSArrayController , the NSTableView can be
manipulated with other objects, such as the NSSearchView (discussed in a
moment), to produce interfaces that integrate smoothly and provide a great
user experience.
With this configuration, the NSTableView displays the data from the NSArrayController
automatically and, thanks to KVO, stays in sync with the data stored in the
persistence layer.
NSArrayController
NSArrayController is an extremely useful object when working with Core Data
because it is aware of the Core Data layer and knows how to talk to it without
any additional code on our part. When we configure it within Interface Builder,
all that we really need to give it is the NSManagedObjectContext and a data object
type. The rest of the work—retrieving the objects, updating those objects, and
creating new ones—is all handled for us.
NSArrayController also understands relationships between objects when it is
working with Core Data. In our recipe application, we have one NSArrayController
configured to manage RecipeIngredient objects. Based on our data model, these
are child objects that are bound to a specific recipe. Because NSArrayController
understands these relationships, we can configure it to pull and display only
those RecipeIngredient objects that are connected to a Recipe object that is
selected in another NSArrayController . This again is made possible by KVC and
KVO. When we configure the RecipeIngredient 's NSArrayController to provide only
those ingredients that are related to the specific recipe, what it is doing behind
the scenes is accessing the Recipe object and requesting its ingredients property
via KVC. In the RecipeIngredient ' s NSArrayController , we bind the NSManagedObjectContext
so that new ingredients can be added. In addition to properly being able to
create (and remove) objects from the persistence layer, the NSArrayController will
also manage the relationship between the newly created or removed RecipeIn-
gredient and the parent Recipe object.
All of this works because Core Data is the entire persistence layer and is
accessed in a consistent way no matter what object is being dealt with.
Because Core Data uses KVO and KVC, our controller objects do not need to
know very much about the objects, other than the name of the objects and
where they are stored. The rest is all resolved at runtime based on the settings