#JSONCodable Hassle-free JSON encoding and decoding in Swift

Swift 2.0 required This project uses a variety of Swift features including Protocol Extensions and Error Handling available in Swift 2.0

JSONCodable is made of two separate protocols JSONEncodable and JSONDecodable. JSONEncodable allows your structs and classes to generate NSDictionary or [String: AnyObject] equivalents for use with NSJSONSerialization. JSONDecodable allows you to generate structs from NSDictionary coming in from a network request for example.

We'll use the following models in this example:

struct User {
    var id: Int = 0
    var name: String = ""
    var email: String?
    var company: Company?
    var friends: [User] = []
}

struct Company {
    var name: String = ""
    var address: String?
}

Using JSONEncodable

Simply add conformance to JSONEncodable (or to JSONCodable):

extension User: JSONEncodable {
    func JSONEncode() throws -> AnyObject {
        var result: [String: AnyObject] = [:]
        try result.archive(id, key: "id")
        try result.archive(name, key: "full_name")
        try result.archive(email, key: "email")
        try result.archive(company, key: "company")
        try result.archive(friends, key: "friends")
        return result
    }
}

extension Company: JSONEncodable {}

The default implementation of func JSONEncode() inspects the properties of your type using reflection (see Company.) If you need a different mapping, you can provide your own implementation (see User.)

Instantiate your struct, then use the func JSONEncode() method to obtain a equivalent form suitable for use with NSJSONSerialization:

let dict = try user.JSONEncode()
print("dict: \(dict)")

Result:

[full_name: John Appleseed, id: 24, email: [email protected], company: {
    address = "1 Infinite Loop, Cupertino, CA";
    name = Apple;
}, friends: (
        {
        friends =         (
        );
        "full_name" = "Bob Jefferson";
        id = 27;
    },
        {
        friends =         (
        );
        "full_name" = "Jen Jackson";
        id = 29;
    }
)]

##Using JSONDecodable

Simply add conformance to JSONDecodable (or to JSONCodable):

extension User: JSONDecodable {
    mutating func JSONDecode(JSONDictionary: [String : AnyObject]) {
        JSONDictionary.restore(&id, key: "id")
        JSONDictionary.restore(&name, key: "full_name")
        JSONDictionary.restore(&email, key: "email")
        JSONDictionary.restore(&company, key: "company")
        JSONDictionary.restore(&friends, key: "friends")
    }
}

extension Company: JSONDecodable {
    mutating func JSONDecode(JSONDictionary: [String : AnyObject]) {
        JSONDictionary.restore(&name, key: "name")
        JSONDictionary.restore(&address, key: "address")
    }
}

Unlike in JSONEncodable, you must provide the implementations for func JSONDecode(). As before, you can use this to configure the mapping between keys in the Dictionary to properties in your structs and classes.

let user = User(JSONDictionary: JSON)
print("\(user)")

Result:

User(
  id: 24,
  name: "John Appleseed",
  email: Optional("[email protected]"),
  company: Optional(Company(
    name: "Apple",
    address: Optional("1 Infinite Loop, Cupertino, CA")
  )),
  friends: [
    User(
      id: 27,
      name: "Bob Jefferson",
      email: nil,
      company: nil,
      friends: []
    ),
    User(
      id: 29,
      name: "Jen Jackson",
      email: nil,
      company: nil,
      friends: []
    )
  ]
)

The convenience initializer init(JSONDictionary: [String: AnyObject]) is provided.

Limitations

1. Your types must be initializable without any parameters, i.e. implement init(). You can do this by either providing a default value for all your properties or implement init() directly and configuring your properties at initialization.

2. You must use var instead of let when declaring properties.

JSONDecodable needs to be able to create new instances of your types and set their values thereafter.

Refer to the included playground for more information.

License

JSONCodable is under the MIT license.