ELCodable

ELCodable, a data model decoding/encoding framework for Swift. Inspired by Anviking's Decodable (https://github.com/Anviking/Decodable)

Introduction

ELCodable provides an easy mechanism by which to encode/decode JSON data into proper swift models w/ data mutability/immutability.

It provides the following functionality:

• Swift optionals to determine required fields from optional fields.
• An easy to use JSON wrapper.
• Encoding to JSON.
• Decoding from JSON.
• Type conversion, both in model types as well as common forms of JSON, such as NSData, Dictionaries, Arrays, etc.
• Data validation.

Defining & using your model

struct MyModel {
    let myString: String
    let myNumber: UInt
}

Once you've defined your model, now extend it such that it works with the decoder.

extension MyModel: Decodable {
    static func decode(json: JSON?) throws -> MyModel {
        return try MyModel(
            myString: json ==> "myString",
            myNumber: json ==> "myNumber"
        )
    }
}

The above will allow your model to be decoded. As for triggering decoding, you've got a few options...

The simplest way:

let myModel = try? MyModel.decode(json)

At this point, myModel will either have a value, or be nil. If you'd like more information on what caused a failure, you can do this:

do {
    // decode the json
    let myModel = try MyModel.decode(json)
    // do something with the model
    doSomething(myModel)
} catch DecodeError.NotFound(let key) {
    print("MyModel couldn't be decoded because \(key) couldn't be found.")
} catch let error {
    // catch all for any errors that may happen.
}

Now that we've decoded and done something with our model. Lets look at how encoding would work.

Encoding

extension MyModel: Encodable {
    func encode() throws -> JSON {
        return try encodeToJSON(
            "myString" <== myString,
            "myNumber" <== myNumber
        )
    }
}

Now that you've done this, you can send it to disk wherever else it might need to go.

let json = try? myModel.encode()
if let json = json {
    json.data().writeToFile(path)
}

Validation

Model decode validation is as easy as adding a call to validateModel(), and writing a validateDecode() function. Validating Encoding works more or less the same way.

extension MyModel: Decodable {
    static func decode(json: JSON?) throws -> MyModel {
        return try MyModel(
            myString: json ==> "myString",
            myNumber: json ==> "myNumber"
        ).validateModel() // triggers validation to occur
    }
    
    func validateDecode() throws -> MyModel {
        if myNumber != 3 {
            throw DecodeError.ValidationFailed
        } else {
            // myNumber is 3, our model is valid.
            return self
        }
    }
}

What about sub-models?

Take this example model:

struct TestModel {
    let aString: String
    let aModelArray: [SubModel]
}

As long as SubModel implements Decodable and/or Encodable, it'll "just work". Validation is left up to the implementor, but it's done the same way regardless of sub-models.

What about fields that aren't necessarily required?

Simply mark them as optionals in your model, like this:

struct TestModel {
    // required
    let aString: String
    // not required
    let aModelArray: [SubModel]?
}

What types can I use in my models?

Model types will typically be Swift types. Things like String, UInt, structs, Dictionary, etc. Because of this, it's not suitable for use with Objective-C directly. It can be done though with a little wrapper. See Decimal.swift, which makes NSDecimalNumber a first class type in Swift.

You may come across other types you'd like to have in your models besides the ones supplied in ELCodable. It's pretty easy to do this, you'd just need to make the type conform to Decodeable and/or Encodable. See below:

extension Bool: Decodable {
    public static func decode(json: JSON?) throws -> Bool {
        if let value = json?.bool {
            return value
        }
        throw DecodeError.Undecodable
    }
}

extension Decimal: Decodable {
    public static func decode(json: JSON?) throws -> Decimal {
        if let value = json?.decimal {
            return Decimal(value)
        }
        throw DecodeError.Undecodable
    }
}

Tell me more about this Decimal type

The Decimal type allows NSDecimalNumber to work and function exactly as a Double or Float would, while preserving the precision within. There's not much to it really, however since numbers tend to be compared to various things, it implements the Equatable protocol and has various operator overloads on ==, <=, >= etc.

Contributions

We appreciate your contributions to all of our projects and look forward to interacting with you via Pull Requests, the issue tracker, via Twitter, etc. We're happy to help you, and to have you help us. We'll strive to answer every PR and issue and be very transparent in what we do.

Electrode-iOS's Primary Contributors

Dr. Sneed (@bsneed)
Steve Riggins (@steveriggins)
Sam Grover (@samgrover)
Angelo Di Paolo (@angelodipaolo)
Cody Garvin (@migs647)

License

The MIT License (MIT)

Copyright (c) 2015 Walmart, WalmartLabs, and other Contributors

Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files (the "Software"), to deal in the Software without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so, subject to the following conditions:

The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software.

THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.