Protocol-Oriented Network abstraction layer written in Swift.





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4yrs ago











Build status Platform iOS Swift 4 compatible Carthage compatible CocoaPods compatible License: MIT

Made with ❤️ by XMARTLABS. View all our open source contributions.


Protocol-Oriented Network abstraction layer written in Swift. Greatly inspired by RxPagination project but working on top of Alamofire and the JSON parsing library of your choice.


  • API abstraction through RouteType conformance.
  • Pagination support through PaginationRequestType conformance.
  • Supports for any JSON parsing library such as Decodable and Argo through OperaDecodable protocol conformance.
  • Networking errors abstraction through OperaError type. OperaSwift OperaError indicates either an NSURLSession error, Alamofire error, or your JSON parsing library error.
  • RxSwift wrappers around Alamofire.Request that return either a Single of a JSON serialized type or an array if it or a completable sequence. NetworkError is passed when error event happens.
  • RxSwift wrappers around PaginationRequestType that return a Single of a PaginationResponseType which contains the serialized elements and information about the current, next and previous page.
  • Ability to easily mock services through RouteType.sampleData.
  • Ability to use multiple RequestAdapters through CompositeAdapter.
  • Easily upload files or images using HTTP multipart requests.
  • Download progress on every RouteType and upload progress on MultipartRouteType.


Route setup

A RouteType is a high level representation of the request for a REST API endpoint. By adopting the RouteType protocol a type is able to create its corresponding request.

import Alamofire
import OperaSwift

// just a hierarchy structure to organize routes
struct GithubAPI {
    struct Repository {}

extension GithubAPI.Repository {

  struct Search: RouteType {

      var method: HTTPMethod { return .get }
      var path: String { return "search/repositories" }

  struct GetInfo: RouteType {

      let owner: String
      let repo: String

      var method: HTTPMethod { return .get }
      var path: String { return "repos/\(owner)/\(repo)" }

Alternatively, you can opt to conform to RouteType form an enum where each enum value is a specific route (api endpoint) with its own associated values.

If you are curious check out the rest of RouteType protocol definition.

As you may have seen, any type that conforms to RouteType must provide baseUrl and the Alamofire manager instance.

Usually these values do not change among our routes so we can provide them by implementing a protocol extension over RouteType as shown below.

extension RouteType {

    var baseURL: URL {
        return URL(string: "https://api.github.com")!

    var manager: ManagerType {
        return Manager.singleton

Now, by default, all RouteTypes we define will provide https://api.github.com as baseUrl and Manager.singleton as mananger. It's up to you to customize it within a specific RouteType protocol conformance.

Default RouteTypes

To avoid having to implement the method property in every RouteType Opera provides A protocol for each HTTPMethod so you can implement those:

protocol GetRouteType: RouteType {}
protocol PostRouteType: RouteType {}
protocol OptionsRouteType: RouteType {}
protocol HeadRouteType: RouteType {}
protocol PutRouteType: RouteType {}
protocol PatchRouteType: RouteType {}
protocol DeleteRouteType: RouteType {}
protocol TraceRouteType: RouteType {}
protocol ConnectRouteType: RouteType {}

They are pretty simple, they only implement the method property of RouteType with the HTTPMethod that matches.

Additional RouteTypes


struct Upload: ImageUploadRouteType {

  let image: UIImage
  let encoding: ImageUploadEncoding = .jpeg(quality: 0.80)
  let path = "/upload"
  let baseURL = URL(string: "...")!


And then use it like this:

Upload(image: UIImage(named: "myImage")!)
    onCompleted: {
      // success :)
    onError: { error in
      // do something when something went wrong

Note: If you want to upload a generic list of files through an HTTP multipart request, use MultipartRouteType instead.

Creating requests

At this point we can easily create an Alamofire Request:

let request: Request =  GithubAPI.Repository.GetInfo(owner: "xmartlabs", repo: "Opera").request

Notice that RouteType conforms to Alamofire.URLConvertible so having the manager we can create the associated Request.

We can also take advantage of the reactive helpers provided by Opera:

    onNext: { (repositories: [Repository]) in
      // do something when networking and Json parsing completes successfully
    onError: {(error: Error) in
      // do something when something went wrong
    onSuccess: { (repositories: [Repository]) in
      // do something when networking and Json parsing completes successfully
    onError: {(error: Error) in
      guard let error = error as? OperaError else {
          //do something when it's not an OperaError
      // do something with the OperaError

If you are not interested in decode your JSON response into a Model you can invoke request.rx.any() which returns an Single of Any for the current request and propagates a OperaError error through the result sequence if something goes wrong.

Error Handling

If you are using the reactive helpers (which are awesome btw!) you can handle the errors on the onError callback which returns an Error that, in case of Networking or Parsing issues, can be casted to OperaError for easier usage. OperaError wraps any error that is Networking or Parsing related. Keep in mind that you have to cast the Error on the onError callback before using it. OperaError also provides a set of properties that make accessing the error's data easier:

    public var error: Error
    public var request: URLRequest?
    public var response: HTTPURLResponse?
    public var body: Any?
    public var statusCode: Int?
    public var localizedDescription: String


    onError: {(error: Error) in
      guard let error = error as? OperaError else {
          //do something when it's not an OperaError
      // do something with the OperaError
      debugPrint("Request failed with status code \(error.statusCode)")

Download & Upload progress

Every RouteType can optionally chain a download progress handler through its reactive extension:

let request: RouteType = ...
  .downloadProgress {
    debugPrint("Download progress: \($0.fractionCompleted)")
    onNext: { (repositories: [Repository]) in
      // do something when networking and Json parsing completes successfully
    onError: {(error: Error) in
      // do something when something went wrong

Only if the routeType is a MultipartRouteType we can also chain an upload progress handler:

ImageUploadRouteType is a specific MultipartRouteType to easily upload images.

  let imageUpload: ImageUploadRouteType = ...
    .uploadProgress {
      debugPrint("Upload progress: \($0.fractionCompleted)")
    .downloadProgress {
      debugPrint("Download progress: \($0.fractionCompleted)")
      onCompleted: {
      onError: { error in


We've said Opera is able to decode JSON response into a Model using your favorite JSON parsing library. Let's see how Opera accomplishes that.

At Xmartlabs we have been using Decodable as our JSON parsing library since March 16. Before that we had used Argo, ObjectMapper and many others. I don't want to deep into the reason of our JSON parsing library choice (we do have our reasons ;)) but during Opera implementation/design we thought it was a good feature to be flexible about it.

This is our Repository model...

struct Repository {

    let id: Int
    let name: String
    let desc: String?
    let company: String?
    let language: String?
    let openIssues: Int
    let stargazersCount: Int
    let forksCount: Int
    let url: NSURL
    let createdAt: NSDate


and OperaDecodable protocol:

public protocol OperaDecodable {
    static func decode(_ json: Any) throws -> Self

Since OperaDecodable and Decodable.Decodable require us to implement the same method, we only have to declare protocol conformance.

// Make Repository conforms to Decodable.Decodable
extension Repository: Decodable {

    static func decode(j: Any) throws -> Repository {
        return try Repository.init(  id: j => "id",
                                   name: j => "name",
                                   desc: j =>? "description",
                                company: j =>? ["owner", "login"],
                               language: j =>? "language",
                             openIssues: j => "open_issues_count",
                        stargazersCount: j => "stargazers_count",
                             forksCount: j => "forks_count",
                                    url: j => "url",
                              createdAt: j => "created_at")

// Declare OperaDecodable adoption
extension Repository : OperaDecodable {}

Using Argo is a little bit harder, we need to implement OperaDecodable in addition to declare the protocol adoption. Here is where swift language protocol extension feature comes in handy....

extension Argo.Decodable where Self.DecodedType == Self, Self: OperaDecodable {
  static func decode(json: Any) throws -> Self {
    let decoded = decode(JSON.parse(json))
    switch decoded {
      case .Success(let value):
        return value
      case .Failure(let error):
        throw error

Now we can make any Argo.Decodable model conform to OperaDecodable by simply declaring OperaDecodable protocol adoption.

extension Repository : OperaDecodable {}

Opera can be used along with RxAlamofire.


Opera represents pagination request through PaginationRequestType protocol which also conforms to URLRequestConvertible. Typically we don't need to create a new type to conform to it. Opera provides PaginationRequest<Element: OperaDecodable> generic type that can be used in most of the scenarios.

One of the requirements to adopt PaginationRequestType is to implement the following initializer:

init(route: RouteType, page: String?, query: String?, filter: FilterType?, collectionKeyPath: String?)

so we create a pagination request doing:

let paginationRequest: PaginationRequest<Repository> = PaginationRequest(route: GithubAPI.Repository.Search(), collectionKeyPath: "items")

Repositories JSON response array is under "items" key as github repositories api documentation indicates so we pass "items" as collectionKeyPath parameter.

A PaginationRequestType wraps up a RouteType instance and holds additional info related with pagination such as query string, page, filters, etc. It also provides some helpers to get a new pagination request from the current pagination request info updating its query string, page or filters value.

let firtPageRequest = paginatinRequest.routeWithPage("1").request
let filteredFirstPageRequest = firtPageRequest.routeWithQuery("Eureka").request

Another variant of the previous helpers is public func routeWithFilter(filter: FilterType) -> Self.

Finally let's look into PaginationViewModel generic class thats allows us to list/paginate/sort/filter decodable items in a very straightforward way.

import UIKit
import RxSwift
import RxCocoa
import Opera

class SearchRepositoriesController: UIViewController {

    @IBOutlet weak var tableView: UITableView!
    @IBOutlet weak var activityIndicatorView: UIActivityIndicatorView!
    @IBOutlet weak var searchBar: UISearchBar!
    lazy var viewModel: PaginationViewModel<PaginationRequest<Repository>> = {
        return PaginationViewModel(paginationRequest: PaginationRequest(route: GithubAPI.Repository.Search(), collectionKeyPath: "items"))

    override func viewDidLoad() {

        // set up views
        tableView.backgroundView = emptyStateLabel
        tableView.keyboardDismissMode = .OnDrag

        // on viewWill appear load pagination view model by emitting false (do not cancel pending
        // request if any) to view model `refreshTrigger` PublishSubject.
        // viewModel is subscribed to `refreshTrigger` observable and starts a new request.
            .map { _ in false }

        // make model view loads next page when reaches table view bottom...  

        // Updates activity indicator accordingly based on modelView `loading` variable.

        // updates tableView observing viewModel `elements`, since github api only works
        // if a query string is present we show no items if the first page is being loading
        // or UISearchBar text is empty.
        // By doing that whenever the search criteria is updated we take away all the item
        // from the table view giving a sense of being fetching/searching the server.
        // Notice the strongly typed `Repository` type below.
        Driver.combineLatest(viewModel.elements.asDriver(), viewModel.firstPageLoading, searchBar.rx.text.asDriver()) { elements, loading, searchText in
                return loading || searchText.isEmpty ? [] : elements
            .drive(tableView.rx.itemsWithCellIdentifier("Cell")) { _, repository: Repository, cell in
                cell.textLabel?.text = repository.name
                cell.detailTextLabel?.text = "🌟\(repository.stargazersCount)"

        // whenever search bar text is changed, wait for 1/4 sec of search bar inactivity
        // then update the `viewModel` pagination request type (will cancel any pending request).
        // We propagates query string by binding it to viewModel.queryTrigger.
            .filter { !$0.isEmpty }
            .throttle(0.25, scheduler: MainScheduler.instance)

        // handles view empty state.
        Driver.combineLatest(viewModel.emptyState, searchBar.rx.text.asDriver().throttle(0.25)) { $0 ||  $1.isEmpty }
            .driveNext { [weak self] state in
                self?.emptyStateLabel.hidden = !state
                self?.emptyStateLabel.text = (self?.searchBar.text?.isEmpty ?? true) ? "Enter text to search repositories" : "No repositories found"

    private lazy var emptyStateLabel: UILabel = {
        let emptyStateLabel = UILabel()
        emptyStateLabel.text = ControllerConstants.NoTextMessage
        emptyStateLabel.textAlignment = .Center
        return emptyStateLabel
    private let disposeBag = DisposeBag()

If you want to continue using the conventional Alamofire way to make requests, Opera makes this easy by providing the following response serializers.

extension Request {
         Generic response object serialization that returns a OperaDecodable instance.

         - parameter keyPath:           keyPath to look up JSON object to serialize. Ignore parameter or pass nil when JSON object is the JSON root item.
         - parameter completionHandler: A closure to be executed once the request has finished.

         - returns: The request.
    public func responseObject<T : OperaDecodable>(keyPath: String? = default, completionHandler: Response<T, OperaError> -> Void) -> Self
         Generic response object serialization that returns an Array of OperaDecodable instances.

         - parameter collectionKeyPath: keyPath to look up JSON array to serialize. Ignore parameter or pass nil when JSON array is the JSON root item.
         - parameter completionHandler: A closure to be executed once the request has finished.

         - returns: The request.
    public func responseCollection<T : OperaDecodable>(collectionKeyPath: String? = default, completionHandler: Response<[T], OperaError> -> Void) -> Self
         Generic response object serialization. Notice that Response Error type is NetworkError.

         - parameter completionHandler: A closure to be executed once the request has finished.

         - returns: The request.
    public func responseAnyObject(completionHandler: Response<AnyObject, OperaError> -> Void) -> Self


Opera provides a way to use multiple RequestAdapter to adapt your requests. The class CompositeAdapter provides a way to setup a pipeline of RequestAdapter that will be applied to your requests.

To use it you just have to create a CompositeAdapter, add all your adapters ad set it as your NetworkManager's adapter.


let adapter = CompositeAdapter()
adapter.append(adapter: KeychainAccessTokenAdapter())
adapter.append(adapter: LanguageAdapter())
manager.adapter = adapter


  • iOS 9.0+ / Mac OS X 10.9+ / tvOS 9.0+ / watchOS 2.0+
  • Xcode 8+

Getting involved

  • If you want to contribute please feel free to submit pull requests.
  • If you have a feature request please open an issue.
  • If you found a bug or need help please check older issues, FAQ and threads on StackOverflow (Tag 'XLOpera') before submitting an issue.

Before contribute check the CONTRIBUTING file for more info.

If you use Opera in your app We would love to hear about it! Drop us a line on twitter.


Follow these 4 steps to run Example project:

  • Clone Opera repository,
  • Run the build_dependencies.sh shell script (you must have carthage installed). Optionally, you can specify the platforms you want to build - iOS, tvOS, OSX - via the --platform parameter.
  • Open Opera workspace
  • Run the Example project.



CocoaPods is a dependency manager for Cocoa projects.

To install Opera, simply add the following line to your Podfile:

pod 'OperaSwift', '~> 3.0'


Carthage is a simple, decentralized dependency manager for Cocoa.

To install Opera, simply add the following line to your Cartfile:

github "xmartlabs/Opera" ~> 3.0


Contributors & Maintainers


How do I set up additional request parameters right before creating Alamofire request from a RouteType or a PaginationRequestType?

By making any of them adopt URLRequestParametersSetup protocol.

 *  By adopting URLRequestParametersSetup a RouteType or PaginationRequestType is able to make a final customization to request parameters dictionary before they are encoded.
public protocol URLRequestParametersSetup {
    func urlRequestParametersSetup(urlRequest: NSMutableURLRequest, parameters: [String: AnyObject]?) -> [String: AnyObject]?

How do I customize NSMutableURLRequest that is not possible through RouteType and PaginationRouteType adoption?

You can setup an Alamofire RequestAdapter on your manager to customize your request right before sending it.

How do I customize the default names and values of parameters for a PaginationRequest?

You can make PaginationRequest adopt PaginationRequestTypeSettings.

 *  By adopting PaginationRequestTypeSettings a PaginationRequestType is able to customize its default parameter names such as query, page and its first page value.
public protocol PaginationRequestTypeSettings {

    var queryParameterName: String { get }
    var pageParameterName: String { get }
    var firstPageParameterValue: String { get }


The default settings by Opera are the following ones:

  • "q" for query
  • "page" for page
  • "1" for firstPageParameterValue

Change Log

This can be found in the CHANGELOG.md file.

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