Codable struct containing default values.

struct-codable-default-optionals.swift

/// This enabled the struct to:
///   - Be auto-decodable via json.
///   - Assign a default value if the property is not present in json.
///   - Assign values via init constructor.
struct MyStruct: Codable, Equatable {

  let propFoo: Bool
  let propBar: Bool

  // Set default values for missing properties
  // {"propFoo": true, "propBar": true} // propBar => true
  // {"propFoo": true} // propBar => false
  init(from decoder: Decoder) throws {
    let container = try decoder.container(keyedBy: CodingKeys.self)
    propFoo = try container.decodeIfPresent(Bool.self, forKey: .propFoo) ?? false
    propBar = try container.decodeIfPresent(Bar.self, forKey: .propBar) ?? false
  }

  // Set custom values via manual constructor
  // MyStruct(propFoo: true, propBar: true)
  init(propFoo: Bool, propBar: Bool) {
    self.propFoo = propFoo
    self.propFoo = propFoo
  }
}