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Data Modeling With Xcode

The purpose of the data modeling tool is to create a data model (or schema) for use with the Core Data framework. Rather than dealing with classes, instance variables, and methods, you use the tool to define entities, the attributes they have, and the relationships between them. For more about entity-relationship modeling, object modeling, why these are important, and definitions of terms (inverse relationship, optional attribute, and so on), see Object Modeling. For more about specific Core Data classes, see the relevant API reference documentation.

Ultimately, at runtime, the model is turned into an instance of NSManagedObjectModel with a collection of NSEntityDescription, NSAttribute, NSRelationship, and NSFetchRequest objects. In some respects this is analogous to the behavior of Interface Builder. With Interface Builder, you graphically create a collection of objects that are then saved in a file (a nib file) and recreated at runtime. As with user interface elements, it is possible to create a model directly in code at runtime; however it is typically easier to do so graphically using the appropriate tool. Similarly, just as it is possible to modify the user interface after it has been loaded, it is also possible to customize a model after it has been loaded. (Note that a model does have a constraint not shared with a nib file: once loaded, a model cannot be modified after it has been used.)

The tool’s basic features and behavior are described in “Common Features of the Xcode Design Tools.” This chapter describes features and behavior that are unique to the data modeler.

Contents:

The Diagram View for Data Modeling
The Model Browser for Data Modeling
The Predicate Builder
Workflow

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