Creating an Core Data Model

Remarks#

Attribute types include: Undefined, Integer 16, Integer 32, Integer 64, Decimal, Double, Float, String, Boolean, Date, Binary, Data, or Transformable

When defining an Entity as abstract you won’t be creating any instances of that entity. For example a Person would be abstract and a Employee or Customer would be a concrete subentities.

Transient attributes are properties that you define as part of the model, but which are not saved to the persistent store as part of an entity instance’s data. Core Data does track changes you make to transient properties, so they are recorded for undo operations. You use transient properties for a variety of purposes, including keeping calculated values and derived values.

The Destination field defines what object (or objects) are returned when the relationship is accessed in code.

The Inverse field defines the other half of a relationship. Because each relationship is defined from one direction, this field joins two relationships together to create a fully bidirectional relationship.

Source: Core Data Programming Guide

Adding an Entity to Core Data Model

First it is important to understand that the Core Data Model is the *.xcdatamodeld file. You will notice you have not entities. You will have to create one yourself. At the bottom of Xcode you will notice a button that says “Add Entity” click it and you will have a new entity in the navigator area for you to work with on the project.

Adding Attributes to Entity

Under the attributes section you add the attributes to your model. This button is a plus located at the bottom of the section. You can add any attributes that are relevant to your app. You have several options of types to choose from ranging from Booleans to Dates and more. The Inspector panel also has several options.

This is the Inspector Panel which allows you to add properties to the Attribute for example if you were adding an email you could provide a regex string ".+@([A-Za-z0-9-]+\\.)+[A-Za-z]{2}[A-Za-z]*" to prevent postal addresses from being added to your email Attribute. Validation could allow for a min and max character for a phone number.

Adding Relationships to Core Data Model

Relationships are relationship between entities that can be one-to-one or one-to-many. Creating a relationship is not needed to use Core Data.