Skip to content
A better way to deal with JSON parsing in Swift.
Ruby Swift Shell
Branch: master
Clone or download
Fetching latest commit…
Cannot retrieve the latest commit at this time.
Type Name Latest commit message Commit time
Failed to load latest commit information.


License Gem Swift

JSONCop makes it easy to write a simple model layer for your Cocoa and Cocoa Touch application.

JSONCop scans all the methods and variables like JSONKeyPathByPropertyKey xxxJSONTransformer in all the structs which declare //@jsoncop before struct declaration line. And it won't change your original project structure.

let json: [String: Any] = [
    "id": 1,
    "name": "Draven",
    "createdAt": NSTimeIntervalSince1970
let person = Person.parse(json: json)


  1. Run cop install in a project root folder
  2. Add //@jsoncop just before model definition line
$ sudo gem install jsoncop --verbose
$ cop install
struct Person {
    let id: Int
    let name: String

Then, each time build action is triggered, JSONCop would generate several parsing methods in swift files.

All the code between // MARK: - JSONCop-Start and // JSONCop-End and will be replaced when re-run cop generate in current project folder. Other codes will remain unchanged. Please don't write any codes in this area.

extension Person {
    static func parse(json: Any) -> Person? {
        guard let json = json as? [String: Any] else { return nil }
        guard let id = json["id"] as? Int,
            let name = json["name"] as? String,
            let projects = (json["projects"] as? [[String: Any]]).flatMap(projectsJSONTransformer) else { return nil }
        return Person(id: id, name: name, projects: projects)
    static func parses(jsons: Any) -> [Person] {
        guard let jsons = jsons as? [[String: Any]] else { return [] }
        return jsons.flatMap(parse)

Checkout JSONCopExample for more information.


  • JSON key to attribute customisation

    struct Person {
        let id: Int
        let name: String
        static func JSONKeyPathByPropertyKey() -> [String: String] {
            return ["name": "nickname"]
  • Value transformer customisation

    struct Person {
        let id: Int
        let name: String
        let gender: Gender
        let projects: [Project]
        enum Gender: Int {
            case male = 0
            case female = 1
        static func genderJSONTransformer(value: Int) -> Gender? {
            return Gender(rawValue: value)
        static func projectsJSONTransformer(value: [[String: Any]]) -> [Project] {
            return value.flatMap(Project.parse)
  • Nested JSON value extraction

    static func JSONKeyPathByPropertyKey() -> [String: String] {
        return ["currentProjectName": ""]


sudo gem install jsoncop --verbose


Bug reports and pull requests are welcome on GitHub at This project is intended to be a safe, welcoming space for collaboration, and contributors are expected to adhere to the Contributor Covenant code of conduct.


The gem is available as open source under the terms of the MIT License.

You can’t perform that action at this time.