Zarra - Core Data in Objective-C

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It is amazing to realize that as of the writing of this book, Core Data is over 12 years old. Thats an amazing number when you consider that its more powerful and more popular today than it has ever been. For a framework, thats pretty spectacular.

If you plan on writing an application that saves data to disk, you should take a very long look at Core Data. Whether youre focusing on the desktop or the iPhone, Core Data is the most efficient solution to data persistence.

A good way to confirm that you know enough Cocoa to benefit from this book is to take a look at Chapter 1, . You may find it dense, but every step should be familiar to you.

In the simplest terms, Core Data is an object graph that can be persisted to disk. But just like describing a man as a bag of mostly water, that description hardly does Core Data justice. If youve worked with Interface Builder (specifically on OS X), you know that it effectively removes a third of the coding from the Model-View-Controller (MVC) design pattern. With Interface Builder, developers dont need to spend countless hours writing and rewriting their user interface to make sure that its pixel perfect. Instead, they simply drag and drop the elements in the IDE, bind them together, and call it done.

Of course, the problem with Interface Builder is that we still need to code the other two parts! Both the controller and the model need to be developed in code and made to work with the interface we just designed. Thats where Core Data comes in. In a nutshell, Core Data deals with a third of that MVC design: Core Data is the model.

Its a common misconception that Core Data is a database API for Cocoa that allows a Cocoa application to store its data in a database. Although that description is factually accurate, Core Data does a lot more. It serves as the entire model layer. Its not just the persistence on disk; its also all the objects in memory that we normally consider to be data objects. If you have experience working with Java, C#, or some other object-oriented language, you know that the data objects take a lot of time to write and that theyre generally very repetitive in nature. Core Data eliminates most, if not all, of that boilerplate code for us and lets us focus on the business logic, or the controller layer, of our application. It does this with an interface thats as easy to use as Interface Builder.