EncodingAndDecoding.md

Encoding and decoding

Codable is a protocol a type can conform to for easy encoding and decoding (serialization and deserialization) of that type. If a type declares that it conforms to Codable, and all it's properties implement Codable (Foundation types typically do), the Swift compiler will automatically generate a protocol implementation.

⚠️ Note: Codable is only available in Swift 4.0 and later

struct Person: Codable {
  let givenName: String
  let surname: String
  let gender: Gender
    
  enum Gender: String, Codable {
    case male
    case female
  }
}

Other nifty stuff includes:

• Automatic handling of optional values
• Support for custom serialization

Decoding a Person from JSON

let json = """
{
  "givenName": "Donald",
  "surname": "Duck",
  "gender": "male"
}
"""

if let person = try? JSONDecoder().decode(Person.self, from: json.data(using: .utf8)!) {
    print(person.givenName) // Donald
    print(person.surname) // Duck
    print(person.gender) // male
}

Encoding a Person to JSON

let person = Person(givenName: "Donald", surname: "Duck", gender: .male)

if let data = try? JSONEncoder().encode(person),
    let json = String(data: data, encoding: .utf8) {
    print(json) // {"surname":"Duck","givenName":"Donald","gender":"male"}
}

Encodable and Decodable

The definition of Codable looks like this:

public typealias Codable = Decodable & Encodable

Codable consists of two protocols: Decodable and Encodable. By conforming to Codable, the type will be both encodable and decodable. If specific support for only encoding or decoding is needed, conforming to either Encodable or Decodable may make more sense than conforming to Codable.

Custom serialization

To be added.