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Code Sample for Leveraging Structs and Generics in the Networking Layer with Swift 4 (An update to objc.io Swift Talk)
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| import Foundation | |
| import UIKit | |
| import PlaygroundSupport | |
| // MARK: HttpMethod | |
| enum HttpMethod<Body> { | |
| case get | |
| case post(Body) | |
| } | |
| extension HttpMethod { | |
| var methodString: String { | |
| switch self { | |
| case .get: return "GET" | |
| case .post: return "POST" | |
| } | |
| } | |
| func map<B>(f: (Body) -> B) -> HttpMethod<B> where B: Encodable { | |
| switch self { | |
| case .get: return .get | |
| case .post(let body): return .post(f(body)) | |
| } | |
| } | |
| } | |
| // MARK: Resource | |
| struct Resource<A> where A: Decodable { | |
| let method: HttpMethod<Data> | |
| let url: URL | |
| let parse: (Data) -> A? = { data in return try? JSONDecoder().decode(A.self, from: data) } | |
| } | |
| extension Resource { | |
| init<T>(method: HttpMethod<T>, url: URL) where T: Encodable { | |
| self.method = method.map { json in try! JSONEncoder().encode(json) } | |
| self.url = url | |
| } | |
| } | |
| // MARK: ImageResource | |
| struct ImageResource { | |
| let url: URL | |
| let method: HttpMethod<Data> | |
| let parse: (Data) -> UIImage? | |
| } | |
| extension ImageResource { | |
| init(imageUrl: URL) { | |
| self.url = imageUrl | |
| self.method = .get | |
| self.parse = { data in return UIImage(data: data) } | |
| } | |
| } | |
| // MARK: Networking | |
| extension URLRequest { | |
| init<A>(resource: Resource<A>) { | |
| self.init(url: resource.url) | |
| httpMethod = resource.method.methodString | |
| if case let .post(data) = resource.method { httpBody = data } | |
| } | |
| init(imageResource: ImageResource) { | |
| self.init(url: imageResource.url) | |
| httpMethod = imageResource.method.methodString | |
| } | |
| } | |
| final class Networking { | |
| func load<A>(resource: Resource<A>, completion: @escaping (A?, URLRequest?, Error?) -> ()) { | |
| let request = URLRequest(resource: resource) | |
| URLSession.shared.dataTask(with: request) { data, response, error in | |
| if let error = error { | |
| completion(nil, request, error) | |
| return | |
| } | |
| completion(data.flatMap(resource.parse), request, nil) | |
| }.resume() | |
| } | |
| func loadImage(resource: ImageResource, completion: @escaping (UIImage?) -> ()) { | |
| let request = URLRequest(imageResource: resource) | |
| URLSession.shared.dataTask(with: request) { data, response, error in | |
| if let error = error { | |
| debugPrint(error) | |
| completion(nil) | |
| return | |
| } | |
| completion(data.flatMap(resource.parse)) | |
| }.resume() | |
| } | |
| } | |
| // Playground | |
| // Get | |
| struct IPAddress: Decodable { | |
| let ip: String | |
| } | |
| let ipResource = Resource<IPAddress>(method: .get, url: URL(string: "https://api.ipify.org/?format=json")!) | |
| Networking().load(resource: ipResource) { ipaddress, _, _ in | |
| guard let ipaddress = ipaddress else { return } | |
| print("\(ipaddress.ip) IP") | |
| } | |
| // Post | |
| struct Company: Decodable { | |
| let name: String | |
| let email: String | |
| } | |
| let request = ["email": "hello@metaltoad.com"] | |
| let companyResource = Resource<Company>(method: .post(request), url: URL(string: "/company/email")!) | |
| Networking().load(resource: companyResource) { company, _, _ in | |
| guard let company = company else { return } | |
| // print(company.name) | |
| } | |
| // Get Image | |
| let imageResource = ImageResource(imageUrl: URL(string: "https://www.staples-3p.com/s7/is/image/Staples/s1000625_sc7")!) | |
| Networking().loadImage(resource: imageResource) { image in | |
| guard let image = image else { return } | |
| image | |
| } | |
| PlaygroundPage.current.needsIndefiniteExecution = true |
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