Overview

Setting up

Installation

• CocoaPods: Instead of pod 'NSRails', use pod 'NSRails/CoreData'.

• If you’re otherwise including NSRails in a workspace with your project, link with the static library created by the NSRailsCD target, rather than just NSRails.

Why is a separate target necessary?

In the NSRails target, NSRRemoteObject inherits from NSObject. But because your CoreData-managed, NSRails-enabled class need to inherit from NSManagedObject, and because Objective-C does not allow multiple inheritance, NSRRemoteObject inherits from NSManagedObject in the CoreData target. NSRRemoteManagedObject is a subclass of NSRRemoteObject with nice CoreData behavior.

Setting a universal context

• You must set your managed object context to your config’s managedObjectContext property so that NSRails can automatically insert or search for CoreData objects when operations require it:

    [[NSRConfig defaultConfig] setManagedObjectContext:<#your MOC#>];
  

Remote ID

• remoteID is used as a “primary key” that NSRails will use to find other instances, etc. This key also validates uniqueness, meaning saving a context with two records of the same type with the same remoteID will fail.

• remoteID must be defined in your *.xcdatamodeld data model file. You should create an abstract entity that defines a remoteID attribute (Integer 16 is fine) and acts as a parent to your other entities:

Differences from NSRRemoteObject

NSRRemoteManagedObject overrides some NSRRemoteObject behavior to make it more CoreData-friendly.

Remote requests

Class

Remote All (index): Each object returned in the array may be an existing or newly inserted managed object. All managed objects will reflect properties set to those returned by your server. Does not save the context.

Object with ID: If request is successful, will attempt to find an existing local object with objectID, and update its properties to the server’s response. If it cannot find an existing local object with that remoteID, will insert a new object into the context, with those properties. Does not save the context.

Instance

Fetch: If successful and changes are present, will save its managed object context.

Create: If successful, will save its managed object context to update changed properties in the server response (like remoteID).

Destroy: If successful, will delete itself from its managed object context and save the context.

Update/Replace: If successful, will save its managed object context. Note: Changes to the local object will remain even if the request was unsuccessful. It is recommended to implement an undo manager for your managed object context to rollback any changes in this case.

Others

objectWithRemoteDictionary: Will attempt to retrieve the object in CoreData whose remoteID matches the object for key id in dictionary.

• If this object is found, will set its properties using dictionary.
• If this object is not found (or there’s no id key), will create & insert a new object using dictionary.

Does not save the context.

remoteDestroyOnNesting: This property leaves your managed object unaffected. You will have to delete it from your context manually if your request was successful.

nestedClassForProperty: Will search your CoreData entity relationships, and if one is found for that property, will return that relationship’s destination class.