Supercharge Swift's Codable implementations with macros.
MetaCodable framework exposes custom macros which can be used to generate dynamic Codable implementations. The core of the framework is Codable() macro which generates the implementation aided by data provided with using other macros.
MetaCodable aims to supercharge your Codable implementations by providing these inbox features:
- Allows custom
CodingKeyvalue declaration per variable, instead of requiring you to write all theCodingKeyvalues withCodedAt(_:)passing single argument. - Allows to create flattened model for nested
CodingKeyvalues withCodedAt(_:)andCodedIn(_:). - Allows to create composition of multiple
Codabletypes withCodedAt(_:)passing no arguments. - Allows to read data from additional fallback
CodingKeys provided withCodedAs(_:_:). - Allows to provide default value in case of decoding failures with
Default(_:). - Allows to create custom decoding/encoding strategies with
HelperCoderand using them withCodedBy(_:). i.e.LossySequenceCoderetc. - Allows specifying different case values with
CodedAs(_:_:)and case value/protocol type identifier type different fromStringwithCodedAs(). - Allows specifying enum-case/protocol type identifier path with
CodedAt(_:)and case content path withContentAt(_:_:). - Allows to ignore specific properties/cases from decoding/encoding with
IgnoreCoding(),IgnoreDecoding()andIgnoreEncoding(). - Allows to use camel-case names for variables according to Swift API Design Guidelines, while enabling a type/case to work with different case style keys with
CodingKeys(_:). - Allows to ignore all initialized properties of a type/case from decoding/encoding with
IgnoreCodingInitialized()unless explicitly asked to decode/encode by attaching any coding attributes, i.e.CodedIn(_:),CodedAt(_:),CodedBy(_:),Default(_:)etc. - Allows to generate protocol decoding/encoding
HelperCoders withMetaProtocolCodablebuild tool plugin fromDynamicCodabletypes.
See the limitations for this macro.
| Platform | Minimum Swift Version | Installation | Status |
|---|---|---|---|
| iOS 13.0+ / macOS 10.15+ / tvOS 13.0+ / watchOS 6.0+ | 5.9 | Swift Package Manager, CocoaPods | Fully Tested |
| Linux | 5.9 | Swift Package Manager | Fully Tested |
| Windows | 5.9.1 | Swift Package Manager | Fully Tested |
The Swift Package Manager is a tool for automating the distribution of Swift code and is integrated into the swift compiler.
Once you have your Swift package set up, adding MetaCodable as a dependency is as easy as adding it to the dependencies value of your Package.swift.
.package(url: "https://github.com/SwiftyLab/MetaCodable.git", from: "1.0.0"),Then you can add the MetaCodable module product as dependency to the targets of your choosing, by adding it to the dependencies value of your targets.
.product(name: "MetaCodable", package: "MetaCodable"),CocoaPods is a dependency manager for Cocoa projects. For usage and installation instructions, visit their website. To integrate MetaCodable into your Xcode project using CocoaPods, specify it in your Podfile:
pod 'MetaCodable'MetaCodable allows to get rid of boiler plate that was often needed in some typical Codable implementations with features like:
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 {
@CodedAt("title")
var name: String
@CodedAt("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
@CodedAt("additionalInfo", "elevation")
var elevation: Double
}You can even minimize further using CodedIn macro since the final CodingKey value is the same as field name:
@Codable
struct Coordinate {
var latitude: Double
var longitude: Double
@CodedIn("additionalInfo")
var elevation: Double
}Provide default value in case of decoding failures.
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 following definition with MetaCodable:
@Codable
struct CodableData {
@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, memberwise initializer can be generated that uses this default value for the field.
@Codable
@MemberInit
struct CodableData {
@Default("some")
let field: String
}The memberwise initializer generated will look like this:
init(field: String = "some") {
self.field = field
}Use or create custom helpers to provide custom decoding/encoding.
Library provides following helpers that address common custom decoding/encoding needs:
LossySequenceCoderto decode only valid data while ignoring invalid data in a sequence, instead of traditional way of failing decoding entirely.ValueCoderto decodeBool,Int,Double,Stringetc. basic types even if they are represented in some other type, i.e decodingIntfrom"1", decoding boolean from"yes"etc.- Custom Date decoding/encoding with UNIX timestamp (
Since1970DateCoder) or date formatters (DateCoder,ISO8601DateCoder). Base64Coderto decode/encode data in base64 string representation.
And more, see the full documentation for HelperCoders for more details.
You can even create your own by conforming to HelperCoder.
Represent data with variations in the form of external/internal/adjacent tagging, with single enum with each case as a variation or a protocol type that varies with conformances across modules.
i.e. while Swift compiler only generates implementation assuming external tagged enums, only following data:
[
{
"load": {
"key": "MyKey"
}
},
{
"store": {
"key": "MyKey",
"value": 42
}
}
]can be represented by following enum with current compiler implementation:
enum Command {
case load(key: String)
case store(key: String, value: Int)
}while MetaCodable allows data in both of the following format to be represented by above enum as well:
[
{
"type": "load",
"key": "MyKey"
},
{
"type": "store",
"key": "MyKey",
"value": 42
}
][
{
"type": "load",
"content": {
"key": "MyKey"
}
},
{
"type": "store",
"content": {
"key": "MyKey",
"value": 42
}
}
]See the full documentation for MetaCodable and HelperCoders, for API details and advanced use cases.
Also, see the limitations.
If you wish to contribute a change, suggest any improvements, please review our contribution guide, check for open issues, if it is already being worked upon or open a pull request.
MetaCodable is released under the MIT license. See LICENSE for details.