Скачать или смотреть How to Convert JSON Array Objects into List Array in Swift 5

Learn how to efficiently transform a JSON array into a list array in Swift 5 by extracting `trialid` values from your data.
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This video is based on the question https://stackoverflow.com/q/69300798/ asked by the user 'John' ( https://stackoverflow.com/u/8196779/ ) and on the answer https://stackoverflow.com/a/69300916/ provided by the user 'vadian' ( https://stackoverflow.com/u/5044042/ ) at 'Stack Overflow' website. Thanks to these great users and Stackexchange community for their contributions.

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How to Convert JSON Array Objects into List Array in Swift 5

In today’s guide, we’ll tackle a common problem faced by many Swift developers: how to convert a JSON array into a list array, specifically focusing on extracting certain values from that JSON data. If you've ever needed to parse JSON and only retrieve specific fields, this guide is for you! Let’s break down the problem and provide a clear solution.

Understanding the Problem

Imagine you have a JSON response from a server that contains multiple objects, each with different attributes. Your goal is to extract just one specific attribute—in this case, trialid—and construct a list array containing these IDs. Here’s an example of the JSON format we’re working with:

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You want your end result to look like this: [27, 33].

Solution Steps

To achieve this extraction efficiently, follow these organized steps:

1. Define Your Struct

First, define a Swift struct that will conform to the Decodable protocol. Note that struct names should start with an uppercase letter, and you should declare struct members as non-optional if the API consistently sends data for them. Here’s how you should define it:

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2. Fetch and Decode the JSON Data

Next, you need to fetch the data from your URL and decode it into an array of your new struct. Make sure to use the correct type for decoding. Use the following code to achieve this:

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3. Extracting the trialid Values

Once you have the data decoded, you can now easily extract the trialid values into a list array using the map function:

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4. Handling Compiler Advice

If you encounter any errors related to closure return types, you can explicitly define the closure type as shown below. This particular step resolves ambiguities during compilation:

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5. Final Considerations

Test Your Code: Always perform testing to ensure everything works as expected.

Documentation: Keep your code well-documented to make it easier for others (and yourself) to understand later.

Conclusion

In this guide, we covered how to convert JSON array objects into a simple list array of trialid values using Swift 5. By clearly defining your structs, appropriately fetching and decoding your JSON data, and effectively using the map function, you can streamline your data manipulation processes. Now you’re all set to tackle JSON transformations in your Swift applications with confidence!

Happy coding!