Core data dao pattern

Question

I'm starting developing for ios, and now i'm studying core-data. One thing was not clear for me, when i was studying a lot of people was managing core-data entitys on the controller. For me this isn't MVC, since core-data is from Model layer.

So i think will be nice to implement core-data using DAO pattern, but before i wanna know if there is any core-data pattern or if there's some cons implementing DAO using core-data?

Answer 1

It is indeed correct to avoid implementing data look-up methods in the controller. This way the philosophy of the MVC design pattern is adhered to: the controller should just be calling high-level "glue" code and therefore acting as a document that describes how the view is interacting with the model.

With regards to persistent objects, there are two main approaches to this:

• Use the ActiveRecord pattern
• Use the Data Access Object pattern.

A Data Access Object (DAO) is an interface dedicated to the persistence of a model/domain object to a data-source.

The ActiveRecord pattern puts the persistence methods on the model object itself, whereas the DAO defines a discrete interface. The advantage of the DAO pattern is:

• Its easy to define another style of persistence, eg moving from a Database to cloud, without changing the interface and thus effecting other classes.

• The persistence concerns are modularized away from the main model object concerns.

The advantage of the ActiveRecord pattern is simplicity.

ActiveRecord for CoreData

At the present time the ActiveRecord pattern seems to be a lot more popular among Objective-C developers. The following project provides ActiveRecord for CoreData: https://github.com/magicalpanda/MagicalRecord

DAO for CoreData

I'm not familiar with a widely used library that provides the DAO pattern for CoreData. However, it could be quite easily applied without the assitance of a library:

• Define all your data methods for a particular entity - findByName, save, delete, etc on a protocol.
• Implement the protocol by calling the appropriate CoreData methods.

NB: The example project for the Typhoon framework will soon include some examples of applying the DAO pattern with CoreData.