Moya As Network Layer With Codable

What is Moya? And Why?

Moya is that we want some network abstraction layer that sufficiently encapsulates actually calling Alamofire directly. It should be simple enough that common things are easy, but comprehensive enough that complicated things are also easy.

Moya's awesome features:

Compile-time checking for correct API endpoint accesses.
Lets you define a clear usage of different endpoints with associated enum values.
Treats test stubs as first-class citizens so unit testing is super-easy.

Table of Contents

What is Moya? And Why?
Moya's awesome features:
Installation
The API
Let's Start With Models
Create API Enum with TargetType
Create our Networkable Delegate
Now, NetworkManager
Note:
Let's Test Our Code
That's It!

Installation

Installation part is described really well on Moya's Github Page.

The API

We will use JSONPlaceholder as our API.

Let's Start With Models

We will use typealias Codable = Encodable & Decodable for out model.

typealias Codable = Encodable & Decodable

struct Post: Codable {

    var userId: Int
    var id: Int
    var title: String
    var body: String

    enum CodingKeys: String, CodingKey {
        case userId, id, title, body
    }
}

Create API Enum with `TargetType`

For keeping the post as easy as possible we will just use 1 POST and 2 GET route.

Let's create API Enum:

enum JSONPlaceHolderAPI {
    case getPost()
    case getPostWith(id: Int)
    case createPost(post: Post)
}

And add Moya's necessary extensions on top of it:

First, baseURL. This is used for our API's base URL:

var baseURL: URL {
    return URL(string: "https://jsonplaceholder.typicode.com")!
}

Next, path. We are using this for defining different routes (e.g. /posts, /comments etc.):

var path: String {
    return "/posts"
}

Next, method. We can define different methods for different funcs:

var method: Moya.Method {
    switch self {
    case .getPost:
        return .get
    case .getPostWith:
        return .get
    case .createPost:
        return .post
    }
}

Next, we need sample Data for testing. We will not cover this on that post. So, let's give it a simple Data():

var sampleData: Data {
    return Data()
}

Next, we need to define our tasks.

We need .requestPlain for getting all Posts.
.requestParameters for getting specific Post.
Lastly, .requestJSONEncodable for creating a Post with our Codable object.

var task: Task {
    switch self {
    case .getPost:
        return .requestPlain
    case .getPostWith(let id):
        return .requestParameters(parameters: ["id": id], encoding: JSONEncoding.default)
    case .createPost(let post):
        return .requestJSONEncodable(post)
    }
}

Last, we need headers. This will be sent with all of our requests:

var headers: [String : String]? {
    return ["Content-type": "application/json; charset=UTF-8"]
}

Create our `Networkable` Delegate

Our NetworkManager will need to conform to Networkable. We will create our protocol like this:

protocol Networkable {
    var provider: MoyaProvider<JSONPlaceHolderAPI> { get }

    func getPosts(completion: @escaping ([Post]?, Error?) -> ())
    func getPostWith(id: Int, completion: @escaping (Post?, Error?) -> ())
    func createPosth(post: Post, completion: @escaping (Post?, Error?) -> ())
}

Now, `NetworkManager`

We will create a NetworkManager object for Dependency Injection. Let's create:

class NetworkManager: Networkable {

    var provider = MoyaProvider<JSONPlaceHolderAPI>(plugins: [NetworkLoggerPlugin(verbose: true)])

    func getPosts(completion: @escaping ([Post]?, Error?) -> ()) {
        provider.request(.getPost()) { (response) in
            switch response.result {
            case .failure(let error):
                completion(nil, error)
            case .success(let value):
                let decoder = JSONDecoder()
                do {
                    let posts = try decoder.decode([Post].self, from: value.data)
                    completion(posts, nil)
                } catch let error {
                    completion(nil, error)
                }
            }
        }
    }

    func getPostWith(id: Int, completion: @escaping (Post?, Error?) -> ()) {
        provider.request(.getPostWith(id: id)) { (response) in
            switch response.result {
            case .failure(let error):
                completion(nil, error)
            case .success(let value):
                let decoder = JSONDecoder()
                do {
                    let post = try decoder.decode(Post.self, from: value.data)
                    completion(post, nil)
                } catch let error {
                    completion(nil, error)
                }
            }
        }
    }

    func createPosth(post: Post, completion: @escaping (Post?, Error?) -> ()) {
        provider.request(.createPost(post: post)) { (response) in
            switch response.result {
            case .failure(let error):
                completion(nil, error)
            case .success(let value):
                let decoder = JSONDecoder()
                do {
                    let post = try decoder.decode(Post.self, from: value.data)
                    completion(post, nil)
                } catch let error {
                    completion(nil, error)
                }
            }
        }
    }
}

TL;DR: We have created a NetworkManager with necessary request funcs and now we can create an object of that class and use it for requesting.

Note:

I am using a Moya plugin for showing all requests and responses on console in that line:

var provider = MoyaProvider<JSONPlaceHolderAPI>(plugins: [NetworkLoggerPlugin(verbose: true)])

This is not necessary on production.

Let's Test Our Code

We can use our NetworkManager like this, (without Dependency Injection):

class ViewController: UIViewController {

    let networkManager = NetworkManager()

    override func viewDidLoad() {
        super.viewDidLoad()

        networkManager.getPosts { (posts, error) in
            if let error = error {
                print(error)
                return
            }
            dump(posts)
        }
    }
}

Note: With dump you can get more stylized version of print.

That's It!

Now you can use Moya.