swift-codable

Encode and decode Swift types using Codable ( Encodable & Decodable ) with JSONEncoder , JSONDecoder , and related APIs. Targets Swift 6.3 / iOS 26+. When all stored properties are themselves Codable , the compiler synthesizes conformance automatically: Prefer Decodable for read-only API responses and Encodable for write-only. Use Codable only when both directions are required. Rename JSON keys without writing a custom decoder by declaring a CodingKeys enum: Every stored property must appear in the enum. Omitting a property from CodingKeys excludes it from encoding/decoding -- provide a default value or compute it separately. Override init(from:) and encode(to:) for transformations the synthesized conformance cannot handle: Use nestedContainer(keyedBy:forKey:) to navigate and flatten nested JSON: Chain multiple nestedContainer calls to flatten deeply nested structures. Also use nestedUnkeyedContainer(forKey:) for nested arrays.