Tuesday, June 25, 2024

Swift JSONDecoder: Access Nested JSON String without Decoding Entire Object

 To access the raw GeoJSON string within a nested part of your server response without decoding the entire structure, you can use the decodeIfPresent(_:forKey:) method of the Decoder object. Here's how you can modify your code:


init(from decoder: Decoder) throws {

  let container = try decoder.container(keyedBy: CodingKeys.self)

  // ... (decode other properties)


  // Access geoJSON as a string without decoding

  geojsonString = try container.decodeIfPresent(String.self, forKey: .geojson)

}


The decodeIfPresent method attempts to decode the value for the specified key and returns it as an optional type. If the key doesn't exist or the decoding fails, it returns nil.

This approach allows you to retrieve the GeoJSON data as a string without creating unnecessary decoded objects or encountering type mismatch errors.


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