If a Swift Type is Codable but has more properties than the JSON type. What happens during the encoding process? Will the json struct not be able to convert into a swift type?

When a Swift type is Codable but has more properties than the JSON type, the encoding process will only include the properties that are present in the JSON. The additional properties in the Swift type will not affect the encoding process. During decoding, if the JSON does not contain some properties that are present in the Swift type, those properties will be set to their default values if they have any, or they will remain uninitialized if they are optional.

This behavior ensures that the JSON can still be converted into the Swift type, even if the JSON does not contain all the properties defined in the Swift type. This is a common scenario when dealing with APIs where the JSON structure might not always match the Swift model exactly.

For more details on Swift's handling of dynamically sized types and memory layout, you can refer to the session Explore Swift performance.