Simplify Your Core Data Models with Composite Attributes

Combine related data into a single, streamlined attribute with Core Data

Core Data is a tool that helps iOS apps save and manage data efficiently. At WWDC 2023, Apple introduced Composite Attributes, a new feature that makes organizing data in Core Data simpler and faster.

Think of a composite attribute like a small container that holds several related pieces of data together, such as a full address (street, city, and postal code). Instead of saving each part in separate places, you can group them into one. This keeps your data model cleaner and easier to work with.

Supported Platforms and OS Versions:

iOS 17.0+ | iPadOS 17.0+ | Mac Catalyst 17.0+ | macOS 14.0+ | 
tvOS 17.0+ | visionOS 1.0+ | watchOS 10.0+

Let’s explore how Composite Attributes can make your app smarter and more efficient.

What Exactly is a Composite Attribute?

A Composite Attribute allows developers to combine multiple attributes into a single logical group without introducing additional entities or relationships. It is essentially a packed structure stored as one attribute, improving storage efficiency while maintaining semantic clarity. This approach keeps the Core Data schema lightweight and more readable. This attribute type is defined using NSCompositeAttributeType and represented by the NSCompositeAttributeDescription class in Core Data.

Key Benefits

1. Storage Efficiency
   Composite attributes reduce the need for multiple columns in the database by storing structured data as a single field.

2. Improved Querying
   Queries can be more straightforward when dealing with structured data, making complex data relationships easier to manage.

3. Code Simplicity
   Accessing the attribute as a single property simplifies model management, making the codebase more intuitive.

Practical Implementation:

Let’s explore a real-world example. Imagine you want to offer discount deals for your products and need an efficient way to manage and track the discounts associated with each product.

1. Create the Product Entity:
   Start by creating an entity called Product in your .xcdatamodeld file, with the necessary attributes (like productID, productName, price, etc).

2. Add a Composite Type:
   To add a composite type, long press the ‘Add Entity’ option in the model file and create a new composite type named Discount.

3. Add Attributes to the Discount Composite Type

   Here, you will define the discount details, such as discountType, discountValue, startDate, endDate, and other relevant information.

4. Add the Composite Attribute to Product:
   Go back to the Product entity and add a new attribute called discountDetails. In the attribute type selection, choose the newly created Discount composite type.

5. Product Entity’s Managed Object Class:
   Your Product entity's Managed Object class will now have a new attribute discountDetails, which will be represented as a dictionary to hold the discount information.

6. Creating and Saving a Product with Discount Details:
   In your code, create a new Product entity, and assign values for the product’s attributes. Then, create a dictionary containing the discount details and assign it to the product.discountDetails attribute. After that, save the product entity with the discount details.

7. Fetching Entities Using Composite Attribute:
   You can easily fetch entities that match specific values in the composite attribute. For example, to find products with a particular discount type or value, use a FetchRequest to filter products based on the discountDetails dictionary values.

Conclusion:

The Composite Attribute is an excellent option for simplifying complex entities like products with discount details. In this case, we have grouped various discount details (e.g., discount type, value, start and end dates) into a single attribute, which keeps the data model more organized and efficient, reducing redundancy and improving performance.

References:

• What's new in Core Data - WWDC23 - Videos - Apple

• NSCompositeAttributeDescription - Apple Documentation