Hey everyone!
I'm excited to introduce my latest project, MetaCodable, a powerful macro library that will help you with all your Codable needs. Using MetaCodable, you can get rid of repetitive boilerplate code that you often have to write. Some of the feature it provides:
Custom `CodingKey` value declaration per variable, instead of requiring you to write for all fields.
i.e. in the official docs, to define custom CodingKey for 2 fields of Landmark type you had to write:
struct Landmark: Codable {
var name: String
var foundingYear: Int
var location: Coordinate
var vantagePoints: [Coordinate]
enum CodingKeys: String, CodingKey {
case name = "title"
case foundingYear = "founding_date"
case location
case vantagePoints
}
}
But with MetaCodable all you have to write is this:
@Codable
struct Landmark {
@CodablePath("title")
var name: String
@CodablePath("founding_date")
var foundingYear: Int
var location: Coordinate
var vantagePoints: [Coordinate]
}
Create flattened model for nested `CodingKey` values.
i.e. in official docs to decode a JSON like this:
{
"latitude": 0,
"longitude": 0,
"additionalInfo": {
"elevation": 0
}
}
You had to write all these boilerplate:
struct Coordinate {
var latitude: Double
var longitude: Double
var elevation: Double
enum CodingKeys: String, CodingKey {
case latitude
case longitude
case additionalInfo
}
enum AdditionalInfoKeys: String, CodingKey {
case elevation
}
}
extension Coordinate: Decodable {
init(from decoder: Decoder) throws {
let values = try decoder.container(keyedBy: CodingKeys.self)
latitude = try values.decode(Double.self, forKey: .latitude)
longitude = try values.decode(Double.self, forKey: .longitude)
let additionalInfo = try values.nestedContainer(keyedBy: AdditionalInfoKeys.self, forKey: .additionalInfo)
elevation = try additionalInfo.decode(Double.self, forKey: .elevation)
}
}
extension Coordinate: Encodable {
func encode(to encoder: Encoder) throws {
var container = encoder.container(keyedBy: CodingKeys.self)
try container.encode(latitude, forKey: .latitude)
try container.encode(longitude, forKey: .longitude)
var additionalInfo = container.nestedContainer(keyedBy: AdditionalInfoKeys.self, forKey: .additionalInfo)
try additionalInfo.encode(elevation, forKey: .elevation)
}
}
But with MetaCodable all you have to write is this:
@Codable
struct Coordinate {
var latitude: Double
var longitude: Double
@CodablePath("additionalInfo", "elevation")
var elevation: Double
}
Provide default value in case of decoding failures and member-wise initializer generated considers these default values.
Instead of throwing error in case of missing data or type mismatch, you can provide a default value that will be assigned in this case. The memberwise initializer generated also uses this default value for the field. The following definition with MetaCodable:
@Codable
struct CodableData {
@CodablePath(default: "some")
let field: String
}
will not throw any error when empty JSON({}) or JSON with type mismatch({ "field": 5 }) is provided. The default value will be assigned in such case. Also, the memberwise initializer generated will look like this:
init(field: String = "some") {
self.field = field
}
Besides these features you can create custom types with your own decoding/encoding strategies and pass those to be used by macros. I hope you find MetaCodable useful. Let me know if you have any suggestions or additional feature request.
Happy coding!
https://swiftylab.github.io/MetaCodable/documentation/metacodable
