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Encountering a `keyNotFound` error while using Google Books API with Swift? Discover how to resolve it by making simple adjustments to your data models!
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This video is based on the question https://stackoverflow.com/q/71742946/ asked by the user 'Jordan' ( https://stackoverflow.com/u/13063657/ ) and on the answer https://stackoverflow.com/a/71743467/ provided by the user 'burnsi' ( https://stackoverflow.com/u/6950415/ ) at 'Stack Overflow' website. Thanks to these great users and Stackexchange community for their contributions.

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Troubleshooting the keyNotFound Error in Swift with Google Books API

If you're working with Swift and trying to fetch data from the Google Books API, you might run into a frustrating error called keyNotFound. This error typically occurs during the JSON decoding process when your expected data structure doesn't match the incoming JSON response. In this guide, we'll explore the root cause of this error and present a step-by-step solution to fix it.

Understanding the keyNotFound Error

The error message you received indicates that the decoding process couldn't find a specific key, in this case, industryIdentifiers, within the JSON structure returned by the API:

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This means that for at least one of the books in the response, there is no value associated with industryIdentifiers, and therefore it cannot be parsed into the VolumeInfo struct.

Quick Look at Your Data Models

It's essential to understand the structure of your data models to identify where the problem lies. Here's a simplified version of your current struct definitions:

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In this model, the industryIdentifiers property is defined as a non-optional array of IndustryIdentifier. This leads to a decoding failure if the API response does not include industryIdentifiers for certain books.

Solution: Make the industryIdentifiers Optional

To solve the keyNotFound error, we need to modify the definition of industryIdentifiers to allow for cases where it may not be present in the API response. You can do this by changing it to an optional array like so:

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Why This Change Works

Optional Handling: By defining industryIdentifiers as an optional, you allow the JSON decoder to skip this property if it's missing without throwing an error.

Flexibility: This change provides more flexibility to your data model, accommodating different types of book entries you might receive from the Google Books API, some of which might not have any industryIdentifiers associated with them.

Implementing the Fix

With this change in place, you shouldn’t encounter the keyNotFound error anymore when running your API calls. Here's a quick reminder of how you’re currently calling the Google Books API:

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

Conclusion

Encountering a keyNotFound error can be frustrating, but with a little adjustment to your data model, you can ensure your app gracefully handles missing data from the API. By making industryIdentifiers optional, your VolumeInfo struct will now accommodate a wider range of book entries without breaking your app.

Remember, when working with external APIs, it’s a good practice to always consider optional properties in your models to prevent such decoding issues from arising.

Now you can continue building your application, confident that you've resolved this pesky error. Happy coding!