Functional Networking - The Director's Cut

This talk presents a set of refactorings that will help make your Swift networking code more functional. It also features a tool, Bow OpenAPI, that generates your network layer from a Swagger/OpenAPI specification file into a Swift Package.

Transcript

1. Functional Networking Tomás Ruiz López Technical Lead at 47 Degrees @tomasruizlopez
2. Functional Networking Tomás Ruiz López Technical Lead at 47 Degrees @tomasruizlopez The director’s cut
3. openapi: "3.0.0" info: title: Blogging platform version: "1.0.0" paths: /articles: get: tags: - Article operationId: getArticlesWithTag parameters: - name: tag in: query required: true schema: type: string responses: '200': description: The list of articles for the specified tag content: application/json: schema: $ref: '#/components/schemas/Articles'
4. openapi: "3.0.0" info: title: Blogging platform version: "1.0.0" paths: /articles: get: tags: - Article operationId: getArticlesWithTag parameters: - name: tag in: query required: true schema: type: string responses: '200': description: The list of articles for the specified tag content: application/json: schema: $ref: '#/components/schemas/Articles'
5. openapi: "3.0.0" info: title: Blogging platform version: "1.0.0" paths: /articles: get: tags: - Article operationId: getArticlesWithTag parameters: - name: tag in: query required: true schema: type: string responses: '200': description: The list of articles for the specified tag content: application/json: schema: $ref: '#/components/schemas/Articles'
6. openapi: "3.0.0" info: title: Blogging platform version: "1.0.0" paths: /articles: get: tags: - Article operationId: getArticlesWithTag parameters: - name: tag in: query required: true schema: type: string responses: '200': description: The list of articles for the specified tag content: application/json: schema: $ref: '#/components/schemas/Articles'
7. components: schemas: Articles: type: array items: $ref: '#/components/schemas/Article' Article: type: object required: - id - title properties: id: type: integer name: type: string
8. components: schemas: Articles: type: array items: $ref: '#/components/schemas/Article' Article: type: object required: - id - title properties: id: type: integer name: type: string
9. components: schemas: Articles: type: array items: $ref: '#/components/schemas/Article' Article: type: object required: - id - title properties: id: type: integer name: type: string
10. func getArticles(withTag tag: String, callback: @escaping (Result<[Article], Error>) !-> Void) { let path = basePath + "/articles" var components = URLComponents(string: path) components!?.queryItems = [URLQueryItem(name: "tag", value: tag)] guard let url = components!?.url else { callback(.failure(NetworkError.malformedURL)) return } var request = URLRequest(url: url) request.httpMethod = "GET" headers.forEach { header in request.setValue(header.value, forHTTPHeaderField: header.key) } send(request: request, callback: callback) }
11. func getArticles(withTag tag: String, callback: @escaping (Result<[Article], Error>) !-> Void) { let path = basePath + "/articles" var components = URLComponents(string: path) components!?.queryItems = [URLQueryItem(name: "tag", value: tag)] guard let url = components!?.url else { callback(.failure(NetworkError.malformedURL)) return } var request = URLRequest(url: url) request.httpMethod = "GET" headers.forEach { header in request.setValue(header.value, forHTTPHeaderField: header.key) } send(request: request, callback: callback) }
12. func getArticles(withTag tag: String, callback: @escaping (Result<[Article], Error>) !-> Void) { let path = basePath + "/articles" var components = URLComponents(string: path) components!?.queryItems = [URLQueryItem(name: "tag", value: tag)] guard let url = components!?.url else { callback(.failure(NetworkError.malformedURL)) return } var request = URLRequest(url: url) request.httpMethod = "GET" headers.forEach { header in request.setValue(header.value, forHTTPHeaderField: header.key) } send(request: request, callback: callback) }
13. func getArticles(withTag tag: String, callback: @escaping (Result<[Article], Error>) !-> Void) { let path = basePath + "/articles" var components = URLComponents(string: path) components!?.queryItems = [URLQueryItem(name: "tag", value: tag)] guard let url = components!?.url else { callback(.failure(NetworkError.malformedURL)) return } var request = URLRequest(url: url) request.httpMethod = "GET" headers.forEach { header in request.setValue(header.value, forHTTPHeaderField: header.key) } send(request: request, callback: callback) }
14. func send(request: URLRequest, callback: @escaping (Result<[Article], Error>) !-> Void) { URLSession.shared.dataTask(with: request) { data, response, error in if let data = data, let response = response as? HTTPURLResponse { switch response.statusCode { case 200 !!..< 300: if let decoded = try? JSONDecoder().decode([Article].self, from: data) { callback(.success(decoded)) } else { callback(.failure(NetworkError.notDecodable)) } default: callback(.failure(NetworkError.malformedURL)) } } else if let error = error { callback(.failure(error)) } }.resume() }
15. func send(request: URLRequest, callback: @escaping (Result<[Article], Error>) !-> Void) { URLSession.shared.dataTask(with: request) { data, response, error in if let data = data, let response = response as? HTTPURLResponse { switch response.statusCode { case 200 !!..< 300: if let decoded = try? JSONDecoder().decode([Article].self, from: data) { callback(.success(decoded)) } else { callback(.failure(NetworkError.notDecodable)) } default: callback(.failure(NetworkError.malformedURL)) } } else if let error = error { callback(.failure(error)) } }.resume() }
16. func send(request: URLRequest, callback: @escaping (Result<[Article], Error>) !-> Void) { URLSession.shared.dataTask(with: request) { data, response, error in if let data = data, let response = response as? HTTPURLResponse { switch response.statusCode { case 200 !!..< 300: if let decoded = try? JSONDecoder().decode([Article].self, from: data) { callback(.success(decoded)) } else { callback(.failure(NetworkError.notDecodable)) } default: callback(.failure(NetworkError.malformedURL)) } } else if let error = error { callback(.failure(error)) } }.resume() }
17. func send(request: URLRequest, callback: @escaping (Result<[Article], Error>) !-> Void) { URLSession.shared.dataTask(with: request) { data, response, error in if let data = data, let response = response as? HTTPURLResponse { switch response.statusCode { case 200 !!..< 300: if let decoded = try? JSONDecoder().decode([Article].self, from: data) { callback(.success(decoded)) } else { callback(.failure(NetworkError.notDecodable)) } default: callback(.failure(NetworkError.malformedURL)) } } else if let error = error { callback(.failure(error)) } }.resume() }
18. func send(request: URLRequest, callback: @escaping (Result<[Article], Error>) !-> Void) { URLSession.shared.dataTask(with: request) { data, response, error in if let data = data, let response = response as? HTTPURLResponse { switch response.statusCode { case 200 !!..< 300: if let decoded = try? JSONDecoder().decode([Article].self, from: data) { callback(.success(decoded)) } else { callback(.failure(NetworkError.notDecodable)) } default: callback(.failure(NetworkError.malformedURL)) } } else if let error = error { callback(.failure(error)) } }.resume() }
19. func send(request: URLRequest, callback: @escaping (Result<[Article], Error>) !-> Void) { URLSession.shared.dataTask(with: request) { data, response, error in if let data = data, let response = response as? HTTPURLResponse { switch response.statusCode { case 200 !!..< 300: if let decoded = try? JSONDecoder().decode([Article].self, from: data) { callback(.success(decoded)) } else { callback(.failure(NetworkError.notDecodable)) } default: callback(.failure(NetworkError.malformedURL)) } } else if let error = error { callback(.failure(error)) } }.resume() }
20. Bow bow-swift.io
21. func send(request: URLRequest, callback: @escaping (Result<[Article], Error>) !-> Void) { URLSession.shared.dataTask(with: request) { data, response, error in if let data = data, let response = response as? HTTPURLResponse { switch response.statusCode { case 200 !!..< 300: if let decoded = try? JSONDecoder().decode([Article].self, from: data) { callback(.success(decoded)) } else { callback(.failure(NetworkError.notDecodable)) } default: callback(.failure(NetworkError.malformedURL)) } } else if let error = error { callback(.failure(error)) } }.resume() } Insufficient abstraction
22. func send<T: Decodable>(request: URLRequest, callback: @escaping (Result<T, Error>) !-> Void) { URLSession.shared.dataTask(with: request) { data, response, error in if let data = data, let response = response as? HTTPURLResponse { switch response.statusCode { case 200 !!..< 300: if let decoded = try? JSONDecoder().decode(T.self, from: data) { callback(.success(decoded)) } else { callback(.failure(NetworkError.notDecodable)) } default: callback(.failure(NetworkError.malformedURL)) } } else if let error = error { callback(.failure(error)) } }.resume() } Insufficient abstraction Parametric polymorphism
23. func dataTask(with request: URLRequest, completion: @escaping (Data?, URLResponse?, Error?) !-> Void) Illegal states Data URLResponse Error nil nil nil nil nil error nil response nil nil response error value nil nil value nil error value response nil value response error
24. func dataTaskADT(with request: URLRequest, completion: @escaping (Either<Error, (Data, URLResponse)>) !-> Void) Illegal states Algebraic Data Types
25. func dataTaskADT(with request: URLRequest, completion: @escaping (Either<Error, (Data, URLResponse)>) !-> Void) Callback-based communication & Side-effects
26. func dataTaskIO(with request: URLRequest) !-> IO<Error, (Data, URLResponse)> Callbacks & Side-Effects Suspension
27. extension URLSession { func dataTaskIO(with request: URLRequest) !-> IO<Error, (Data, URLResponse)> { IO.async { callback in self.dataTask(with: request) { data, response, error in if let data = data, let response = response { callback(.right((data, response))) } else if let error = error { callback(.left(error)) } }.resume() }^ } }
28. func send<T: Decodable>(request: URLRequest) !-> IO<Error, T> { URLSession.shared.dataTaskIO(with: request) .flatMap { response, data in guard let response = response as? HTTPURLResponse else { return IO.raiseError(NetworkError.malformedURL) } switch response.statusCode { case 200 !!..< 300: return JSONDecoder().safeDecode(T.self, from: data) default: return IO.raiseError(NetworkError.malformedURL) } }^ } Global dependencies
29. func send<T: Decodable>(request: URLRequest, session: URLSession, decoder: SafeDecoder) !-> IO<Error, T> Global dependencies Explicit dependencies
30. func send<T: Decodable>(request: URLRequest, config: APIConfig) !-> IO<Error, T> Global dependencies Explicit dependencies
31. func send<T: Decodable>(request: URLRequest) !-> (APIConfig) !-> IO<Error, T> Global dependencies Explicit dependencies
32. func send<T: Decodable>(request: URLRequest) !-> EnvIO<APIConfig, Error, T> Global dependencies Environmental Effects
33. func send<T: Decodable>(request: URLRequest) !-> IO<Error, T> func send<T: Decodable>(request: URLRequest, session: URLSession, decoder: SafeDecoder) !-> IO<Error, T> func send<T: Decodable>(request: URLRequest, config: APIConfig) !-> IO<Error, T> func send<T: Decodable>(request: URLRequest) !-> (APIConfig) !-> IO<Error, T> func send<T: Decodable>(request: URLRequest) !-> EnvIO<APIConfig, Error, T> Global dependencies Environmental Effects
34. func send<T: Decodable>(request: URLRequest) !-> EnvIO<APIConfig, Error, T> { EnvIO { config in config.session.dataTaskIO(with: request) .flatMap { response, data in guard let response = response as? HTTPURLResponse else { return IO.raiseError(NetworkError.malformedURL) } switch response.statusCode { case 200 !!..< 300: return config.decoder.safeDecode(T.self, from: data) default: return IO.raiseError(NetworkError.malformedURL) } }^ } } Global dependencies Environmental Effects
35. Bow Open Api openapi.bow-swift.io
36. OpenAPI.yaml bow-openapi Swift Package
37. brew tap bow-swift/bow brew install bow-openapi bow-openapi "#name MyAPI "#schema Swagger.json "#output ./MyAPI Install Run
38. import MyAPI let articlesRequest = API.articles.getArticles() Using generated code
39. let config = API.Config(basePath: “https:!//url-to-my-server.com") let articles = try? articlesRequest.provide(config).unsafeRunSync() articlesRequest.provide(config).unsafeRunAsync { either in either.fold({ httpError in !/* !!... !*/ }, { articles in !/* !!... !*/ }) } Running a request
40. import MyAPITest func testEmptyResponse() { let successConfig = API.Config(basePath: "https:!//url-to-my-server.com") .stub(json: "[]", code: 200) let expected = [] assert(API.article.getArticles(), withConfig: successConfig, succeeds: expected, "An empty array was expected") } func testContentResponse() { let successConfig = API.Config(basePath: "https:!//url-to-my-server.com") .stub(contentsOfFile: fileURL, code: 200) let expected = [ Article(identifier: 1234, title: "Intro to Bow OpenAPI") ] assert(API.article.getArticles(), withConfig: successConfig, succeeds: expected, "An array with a single element was expected") } Testing a request
41. import MyAPITest func testEmptyResponse() { let successConfig = API.Config(basePath: "https:!//url-to-my-server.com") .stub(json: "[]", code: 200) let expected = [] assert(API.article.getArticles(), withConfig: successConfig, succeeds: expected, "An empty array was expected") } func testContentResponse() { let successConfig = API.Config(basePath: "https:!//url-to-my-server.com") .stub(contentsOfFile: fileURL, code: 200) let expected = [ Article(identifier: 1234, title: "Intro to Bow OpenAPI") ] assert(API.article.getArticles(), withConfig: successConfig, succeeds: expected, "An array with a single element was expected") } Testing a request
42. import MyAPITest func testEmptyResponse() { let successConfig = API.Config(basePath: "https:!//url-to-my-server.com") .stub(json: "[]", code: 200) let expected = [] assert(API.article.getArticles(), withConfig: successConfig, succeeds: expected, "An empty array was expected") } func testContentResponse() { let successConfig = API.Config(basePath: "https:!//url-to-my-server.com") .stub(contentsOfFile: fileURL, code: 200) let expected = [ Article(identifier: 1234, title: "Intro to Bow OpenAPI") ] assert(API.article.getArticles(), withConfig: successConfig, succeeds: expected, "An array with a single element was expected") } Testing a request
43. Bow vs. Combine Works in earlier versions of iOS and macOS Lazyness guarantees referential transparency
44. Bow vs. Combine io.retry(Schedule.exponential(.milliseconds(250)) .and(Schedule.recurs(8))) publisher.retry(10) Composable and powerful retrial policies io.retry(Schedule.recurs(10))
45. API.user.getMyProfile().flatMap { profile in API.article.getArticles(withTag: "featured").flatMap { articles in makeHome(for: profile, with: articles) } } Bow vs. Combine Convenient imperative-style syntax
46. binding( user !<- API.user.getMyProfile(), articles !<- API.article.getArticles(withTag: "featured"), home !<- makeHome(for: user.get, with: articles.get), yield: home.get) Bow vs. Combine Convenient imperative-style syntax
47. binding( user !<- API.user.getMyProfile(), (featured, news) !<- parallel(API.article.getArticles(withTag: "featured"), API.article.getArticles(withTag: "news")), home !<- makeHome(for: user.get, with: featured.get + news.get), yield: home.get) Bow vs. Combine Convenient imperative-style syntax
48. Conclusion FP Bow bow-swift.io Bow Open Api openapi.bow-swift.io
49. Functional Networking Tomás Ruiz López Technical Lead at 47 Degrees @tomasruizlopez The director’s cut