Combine 🚜 - driven REST API client, based on Alamofire 🔥

What's New

Videre majus quiddam

  • Added Github Actions
  • Swift 5.6

swift workflow

Legatus 🏇

A legatus (anglicised as legate) was a high-ranking Roman military officer in the Roman Army, equivalent to a modern high-ranking general officer. Initially used to delegate power, the term became formalised under Augustus as the officer in command of a legion. Legatus was also a term for an ambassador of the Roman Republic who was appointed by the senate for a mission (legatio) to a foreign nation, as well as for ambassadors who came to Rome from other countries.

Intro 🎬

The basic idea of Legatus is that we want some network abstraction layer that sufficiently encapsulates actually calling Alamofire directly.

Also, it would be cool to have network layer, that will compatible with SwiftUI out-of-the-box 📦, isn't it?🧐

Luckily, Legatus was implemented with Combine framework and have couple of fancy methods, that will allow you to assign(to:on:) your response models right to @Published properties. Neat!🤩

Some awesome features of Legatus🌟:

  • SOLID design (e.g.: APIClient don't stores and configures requests, each request is encapsulated in separate entity).
  • Easy retrying of requests.
  • Elegant and flexible canceling of requests.
  • Reachability tracking.
  • Support JSON and XML response formats.
  • Combine extension.
  • Swift Concurrency support.

Legatus is inspired by Moya.

Project Status 🤖

I consider it's ready for production use.
Any contributions (pull requests, questions, propositions) are always welcome!😃

Requirements 📝

  • Swift 5.6+
  • macOS 12+
  • iOS 15+
  • tvOS 15+
  • watchOS 8+

Installation 📦

  • Swift Package Manager

You can use Xcode SPM GUI: File -> Swift Packages -> Add Package Dependency -> Pick 2.0.1 release (or main branch).

Or add the following to your Package.swift file:

.package(url: "https://github.com/artemkalinovsky/Legatus.git", exact: Version("2.0.1"))

and then specify "Legatus" as a dependency of the Target in which you wish to use Legatus. Here's an example PackageDescription :

// swift-tools-version:5.6
import PackageDescription

let package = Package(
    name: "MyPackage",
    products: [
            name: "MyPackage",
            targets: ["MyPackage"]),
    dependencies: [
        .package(url: "https://github.com/artemkalinovsky/Legatus.git", exact: Version("2.0.1")
    targets: [
            name: "MyPackage",
            dependencies: ["Legatus"])

Basic Usage 🧑‍💻

Let's suppose we want to fetch list of users from JSON and response is look like this:

  • Setup

  1. Create APIClient :
    let apiClient = APIClient(baseURL: URL(string: "https://webservice.com/api/")!)
  1. Create response model:
import Foundation
import Legatus

final class User: Decodable {
    let firstName: String?
    let lastName: String?
    let email: String?

    enum CodingKeys: String, CodingKey {
        case name
        case email

    enum NameKeys: String, CodingKey {
        case firstName = "first"
        case lastName = "last"

    init(from decoder: Decoder) throws {
        let values = try decoder.container(keyedBy: CodingKeys.self)
        email = try values.decodeIfPresent(String.self, forKey: .email)

        let name = try values.nestedContainer(keyedBy: NameKeys.self, forKey: .name)
        firstName = try name.decodeIfPresent(String.self, forKey: .firstName)
        lastName = try name.decodeIfPresent(String.self, forKey: .lastName)
  1. Create request with endpoint path and desired reponse deserializer:
import Foundation
import Legatus

final class UsersApiRequest: DeserializeableRequest {

    var path: String {
    var deserializer: ResponseDeserializer<[User]> {
        JSONDeserializer<User>.collectionDeserializer(keyPath: "results")

  • Perfrom created request

    apiClient.executeRequest(request: UsersApiRequest()) { result in }


Advanced Usage 🤓💻

  • Working with CoreData models.

To deserialize your response right to CoreData NSManagedObject , just call designated initializer firstly:

import Foundation
import CoreData
import Legatus

public class CoreDataObject: NSManagedObject, Decodable {

    required convenience public init(from decoder: Decoder) throws {
        self.init(context: NSManagedObjectContext(concurrencyType: .mainQueueConcurrencyType))

        //TODO: implement decoding

  • Working with Realm models.

To deserialize your response right to Realm Object subclass:

import Foundation
import RealmSwift
import Legatus

final class RealmObject: Object, Decodable {

    @objc dynamic var name = ""

    required init() {

    convenience init(from decoder: Decoder) throws {

        //TODO: implement decoding

Same functionality available for XMLDeserializer too.

  • Retrying requests

If you want to retry previously failed request, just provide count of desiried retry times:

    apiClient.executeRequest(request: UsersApiRequest(), retries: 3) { result in }
  • Request cancelation

To cancel certain request, you have to store it's cancelation token and call cancel() method.

    let cancelationToken = apiClient.executeRequest(request: UsersApiRequest()) { result in }
    DispatchQueue.main.asyncAfter(deadline: .now() + .milliseconds(300)) {

Also, you can cancel all active requests:


Combine Extension 🚜

While working with SwiftUI, where most of UI updates based on Combine mechanisms under the hood, it's very convenient to get Publisher as request result for future transformations and assigns:

    @Published var users = [User]()
    var subscriptions = Set<AnyCancellable>()

         .responsePublisher(request: UsersApiRequest())
         .catch { _ in return Just([User]())}
         .assign(to: \.users, on: self)
         .store(in: &subscriptions)

Swift Concurrency Extension 🚦

    do {
        let usersResponse = try await apiClient.executeRequest(request: UsersApiRequest())
    } catch {
        // handle error

Apps using Legatus 📱

Credits 👏

License 📄

Legatus is released under an MIT license. See LICENCE for more information.


  • Swift Tools 5.6.0
View More Packages from this Author


Last updated: Thu Nov 10 2022 13:46:13 GMT-0500 (GMT-05:00)