simple but full featured http client based on Rx

http-client.swift

import Foundation
import RxSwift
import RxCocoa


class HTTPClient {

    private let session = URLSession.shared

    func request(_ method: String = "GET", url: String,
                 params: [String: String]? = nil, headers: [String: String]? = nil) -> URLRequest? {
        guard let fullURL = { () -> URL? in
            if let params = params, var urlComps = URLComponents(string: url) {
                urlComps.queryItems = params.map { URLQueryItem(name: $0.key, value: $0.value) }
                return urlComps.url
            } else {
                return URL(string: url)
            }
        }() else { return nil }
        var req = URLRequest(url: fullURL)
        req.httpMethod = method
        if let headers = headers {
            for (k, v) in headers {
                req.addValue(v, forHTTPHeaderField: k)
            }
        }
        return req
    }

    func task(request: URLRequest) -> Observable<Data> {
        return Observable.deferred { self.session.rx.data(request: request) }
    }

    func task<T: Codable>(request: URLRequest, decodeWith: T.Type) -> Observable<T> {
        return task(request: request).map { data in
            let decoder = JSONDecoder()
            return try decoder.decode(T.self, from: data)
        }
    }

}