How to Retrieve Values from CKRecord.Reference in CloudKit Efficiently

Описание: Learn how to fetch user details from a CKRecord.Reference in CloudKit without unnecessary data retrieval. Step-by-step guide and code examples provided.
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This video is based on the question https://stackoverflow.com/q/65005987/ asked by the user 'Faruuq' ( https://stackoverflow.com/u/14579941/ ) and on the answer https://stackoverflow.com/a/65009029/ provided by the user 'Kevvv' ( https://stackoverflow.com/u/10116367/ ) at 'Stack Overflow' website. Thanks to these great users and Stackexchange community for their contributions.

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Understanding CKRecord References in CloudKit

When working with CloudKit in Swift, you might find yourself needing to access related data stored in different records. A common scenario arises when you have one record type that references another — for example, a request record that references userDetails. This raises a crucial question: How can you effectively retrieve the referenced user's details without making multiple database fetch calls?

In this guide, we'll explore a practical solution to this problem, giving you all the essential tools to access your user data efficiently.

The Problem

You have two record types in your CloudKit database:

userDetails: Holds individual user information, such as userName

request: Includes a reference to a userDetails record

You want to fetch the details from the request record, specifically the user's name, which exists only in the userDetails record. You've attempted a fetch based on the reference but ran into an issue when trying to access the userName, resulting in an error. Below, we’ll analyze that problem and guide you towards the right solution.

The Incorrect Approach

Here's the code snippet you initially tried to use:

[[See Video to Reveal this Text or Code Snippet]]

The error you encountered was due to attempting to use value(forKey:) on recordID, which does not contain the userName directly — hence the NSUnknownKeyException. So, what can you do instead?

The Correct Approach

Instead of fetching directly for the userName using the reference, you can use that reference to perform a new query to retrieve the details you need. Here’s how to do it step-by-step:

Step 1: Fetch the Request Record

First, you need to retrieve the request record using its recordID:

[[See Video to Reveal this Text or Code Snippet]]

Step 2: Extract the Reference

Next, extract the requesterReferenceId reference from the fetched record:

[[See Video to Reveal this Text or Code Snippet]]

Step 3: Create a Query for User Details

You can now create a query to fetch the details from the userDetails using the retrieved reference:

[[See Video to Reveal this Text or Code Snippet]]

Step 4: Customize the Query

Specify the keys you would like to retrieve from the userDetails record:

[[See Video to Reveal this Text or Code Snippet]]

Step 5: Handle Query Results

Finally, add blocks to handle the results of the query after it’s executed:

[[See Video to Reveal this Text or Code Snippet]]

Conclusion

By following the steps outlined above, you can successfully access the userName and other details from the referenced userDetails record, while avoiding unnecessary data fetching. This organized approach not only improves efficiency but also helps to maintain clarity in your codebase.

With this understanding of using references in CloudKit, you’ll be able to navigate your database more effectively and retrieve the information you need with ease.

If you have any further questions or need additional assistance, feel free to reach out! Happy coding!