Matteo Manferdini

Matteo has been developing apps for iOS since 2008. He has been teaching iOS development best practices to hundreds of students since 2015 and he is the developer of Vulcan, a macOS app to generate SwiftUI code. Before that he was a freelance iOS developer for small and big clients, including TomTom, Squla, Siilo, and Layar. Matteo got a master's degree in computer science and computational logic at the University of Turin. In his spare time he dances and teaches tango.

AsyncImage in SwiftUI: Loading Images from URLs [with Caching]

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AsyncImage is a convenient SwiftUI view that loads remote images using a URL. It’s especially useful in apps that interact with REST APIs since images are usually referenced using URLs in JSON data.

While Apple’s documentation might lead you to believe that AsyncImage caches the downloaded images, that is not the case. If you need image caching, you must implement your own custom solution.

Parsing JSON in Swift: The Complete Guide [With Examples]

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Parsing JSON data is fundamental to any iOS app that performs remote REST API calls.

Thanks to the Codable protocols introduced in Swift 4, Swift has a native and idiomatic way to parse JSON data.

Paired with the JSONDecoder class, the Decodable protocol allows straightforward JSON decoding in a few lines of code and more sophisticated techniques to handle all the possible data formats and edge cases.

Decoding JSON with Dynamic Types in Swift [With Codable]

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JSON data is not always homogenous. There are instances in which a JSON object field can contain objects containing different information.

In such cases, the Swift type for the decoding must be determined dynamically.

Decode JSON with Dynamic Keys in Swift [Dictionaries and Arrays]

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JSON object with dynamic keys presents a specific challenge when decoding data in Swift because stored properties cannot represent dynamic keys.

However, it’s still possible to decode JSON with dynamic keys using the Decodable protocol into dictionaries or arrays by implementing structures that conform to the CodingKey protocol.

Decoding and Flattening Nested JSON with Codable

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JSON data is rarely flat and often contains nested objects.

Nested JSON data can be decoded in Swift using the Decodable protocol and the JSONDecoder class.

However, how you decode nested JSON objects depends on the final result you want to obtain.

Coding Keys in Swift with Decodable: How and When to Use Them

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You can easily parse JSON data in Swift by creating a Decodable type that matches the structure of a JSON object.

However, we often need to decode JSON data that does not match the model types of our apps. In those cases, we need to control the decoding using coding keys.

Parse JSON from an API URL in Swift [Codable and URLSession]

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Fetching and parsing the JSON data returned by a URL is straightforward in Swift, thanks to the JSONDecoder and URLSession classes of the Foundation framework.