How to Fix keyNotFound Error in Swift Storyboard Decoding JSON Data

Learn how to troubleshoot the `keyNotFound` error when decoding JSON data in Swift, and discover how to properly display the data in your app.
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How to Fix keyNotFound Error in Swift Storyboard Decoding JSON Data

When working with Swift and JSON data, developers often encounter various errors during the decoding process. One common error is the keyNotFound error, which can be particularly frustrating. In this guide, we will explore what this error means, why it appears, and how to resolve it effectively.

Understanding the keyNotFound Error

The keyNotFound error strikes when the Swift JSON decoder attempts to decode data but cannot find the expected key in the JSON response. For example, if your JSON structure anticipates a key like "topic", but that key is absent in the data retrieved from the server, you will receive an error similar to this:

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

This error typically indicates that the JSON response structure does not match the expectations set in your Swift models.

Example Code Explanation

Let’s consider the initial code that produced the keyNotFound error:

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

In this model, you explicitly declared the topic property. However, if the received JSON does not contain this key, the error will arise.

Initial Code Snippet

Here's a simplified version of the problematic approach in your code:

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

The core issue lies in how your data model (JSONTest) aligns with the JSON structure.

The Solution: Adjusting Your Code

After diagnosing the issue, let's go through the changes that led to the successful decoding of the JSON response.

Revised Code Structure

Your final working code included a correction in how the JSON structure was interpreted. Here’s the updated version:

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Now, the data is nested under a key scrims. This means your JSON should resemble the following format:

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Updating the View Controller

You would also need to modify how you read data from the JSON:

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Displaying Data on UI Labels

Lastly, to display the decoded information in UI labels, make sure to update your UI elements accordingly. For example:

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Conclusion

Fixing the keyNotFound error involves ensuring that your Swift data models correctly reflect the structure of the incoming JSON. Always confirm that the keys you expect are present in the data you receive from your server. With these steps, you should be able to tackle the keyNotFound error effectively!

If you have any further issues or questions regarding similar errors, feel free to reach out!