Скачать или смотреть Decoding Flat JSON to Nested Structure in Swift

Learn how to effectively decode flat JSON into a nested structure in Swift. In this guide, we explore how to handle common decoding errors and build a well-structured model.
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Decoding Flat JSON to Nested Structure in Swift

When working with APIs, you may often encounter flat JSON structures that need to be decoded into a more complex, nested format in your iOS applications. This can be a bit tricky, especially if your JSON does not match the exact structure of your data models. In this guide, we’re going to tackle the problem of how to decode a flat JSON object into a nested Swift structure. Let's walk through a practical example together.

The Problem

You have the following JSON structure that you want to decode into a specific nested structure:

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

From this JSON, you want to create the following Swift structures:

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

However, while writing your decoding logic, you run into a KeyNotFound error because the JSON does not contain a data key.

Understanding the Issue

The KeyNotFound error indicates that your JSON's structure does not match the expected structure you've created in your Swift models. Specifically, it seems that the UserData is expected to be nested within a data key, which it isn't.

To resolve this issue, we will need to customize the decoding for the Response struct.

The Solution

Step-by-step Guide

Here's how you can decode the JSON into the desired data structure without running into the KeyNotFound error:

Define Your Models: Start with your basic UserData and Response structs, ensuring they conform to the Decodable protocol.

Implement Custom Decoding in the Response Struct: Because the data is flat, we will use a custom initializer in the Response struct to decode the values correctly.

Here’s the complete code:

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

Breakdown of the Code

UserData Struct: This struct simply represents the user details and is straightforward to decode.

Response Struct:

The CodingKeys enum defines the keys for the parts of the Response struct that are present in the JSON.

The custom initializer uses singleValueContainer() to access all keys in the JSON, allowing us to get a UserData object by decoding it directly from this container.

Example Usage

After defining your structs, you can decode the JSON string like so:

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

Conclusion

By using a custom decoding strategy, you can effectively handle flat JSON data and map it to a nested structure in Swift. Understanding how to manipulate the decoding process with custom initializers and containers is essential when working with APIs.

If you follow the steps outlined above, you should be able to decode any flat JSON structure into your desired nested model successfully. Happy coding!