Swift Codable

Encode and decode Swift types with Codable (Encodable & Decodable). Covers custom keys, date/data strategies, polymorphic decoding, default values, and persistence compatibility. Targets Swift 6.3 / iOS 26+.

Contents

• Basic Conformance & CodingKeys
• Decoder Strategies
• Custom Encoding & Decoding
• Polymorphic & Lossy Decoding
• SwiftData & Persistence Boundaries
• Common Mistakes
• Review Checklist
• References

Basic Conformance & CodingKeys

Map serialized JSON field names to Swift property names using CodingKey: