Malibu is a networking library built on promises

Description

Palm trees, coral reefs and breaking waves. Welcome to the surf club Malibu, a networking library built on promises. It's more than just a wrapper around URLSession, but a powerful framework that helps to chain your requests, validations and request processing.

Using When under the hood, Malibu adds a lot of sugar helpers and moves your code up to the next level:

No more "callback hell".
Your requests are described in one place.
Response processing could be easily broken down into multiple logical tasks.
Data and errors are handled separately.
Your networking code is much cleaner, readable and follows DRY principle.

Equip yourself with the necessary gears of Malibu, become a big wave surfer and let the days of shark infested asynchronous networking be a thing of the past. Enjoy the ride!

Catching the wave

You can start your ride straight away, not thinking about configurations:

[Board] in // Let's say we use https://github.com/zenangst/Tailor for mapping return try dictionary.relationsOrThrow("boards") as [Board] }) .done({ boards in // Handle response data }) .fail({ error in // Handle errors }) .always({ _ in // Hide progress bar }) ">

// Create your request => GET http://sharkywaters.com/api/boards?type=1
let request = Request.get("http://sharkywaters.com/api/boards", parameters: ["type": 1])

// Make a call
Malibu.request(request)
  .validate()
  .toJsonDictionary()
  .then({ dictionary -> [Board] in
    // Let's say we use https://github.com/zenangst/Tailor for mapping
    return try dictionary.relationsOrThrow("boards") as [Board]
  })
  .done({ boards in
    // Handle response data
  })
  .fail({ error in
    // Handle errors
  })
  .always({ _ in
    // Hide progress bar
  })

If you still don't see any benefits, keep scrolling down and be ready for even more magic 😉 ...

RequestConvertible

Most of the time we need separate network stacks to work with multiple API services. It's super easy to archive with Malibu. Create an enum that conforms to RequestConvertible protocol and describe your requests with all the properties:

enum SharkywatersEndpoint: RequestConvertible {
  // Describe requests
  case fetchBoards
  case showBoard(id: Int)
  case createBoard(type: Int, title: String)
  case updateBoard(id: Int, type: Int, title: String)
  case deleteBoard(id: Int)

  // Every request will be scoped by the base url
  // Base url is recommended, but optional
  static var baseUrl: URLStringConvertible? = "http://sharkywaters.com/api/"

  // Additional headers for every request
  static var headers: [String: String] = [
    "Accept" : "application/json"
  ]

  // Build requests
  var request: Request {
    switch self {
    case .fetchBoards:
      return Request.get("boards")
    case .showBoard(let id):
      return Request.get("boards/\(id)")
    case .createBoard(let type, let title):
      return Request.post("boards", parameters: ["type": type, "title": title])
    case .updateBoard(let id, let title):
      return Request.patch("boards/\(id)", parameters: ["title": title])
    case .deleteBoard(let id):
      return Request.delete("boards/\(id)")
    }
  }
}

Note that Accept-Language, Accept-Encoding and User-Agent headers are included automatically.

Request

Request is described with a struct in Malibu:

let request = Request(
  // HTTP method
  method: .get,
  // Request url or path
  resource: "boards",
  // Content type
  contentType: .query,
  // Request parameters
  parameters: ["type": 1, "text": "classic"],
  // Headers
  headers: ["custom": "header"],
  // Offline storage configuration
  storePolicy: .unspecified,
  // Cache policy
  cachePolicy: .useProtocolCachePolicy)

There are also multiple helper methods with default values for every HTTP method:

// GET request
let getRequest = Request.get("boards")

// POST request
let postRequest = Request.post(
  "boards",
  // Content type is set to `.json` by default for POST
  contentType: .formURLEncoded,
  parameters: ["type" : kind, "title" : title])

// PUT request
let putRequest = Request.put("boards/1", parameters: ["type" : kind, "title" : title])

// PATCH request
let patchRequest = Request.patch("boards/1", parameters: ["title" : title])

// DELETE request
let deleteRequest = Request.delete("boards/1")

URLSessionDataTask is default for executing requests. For uploading there are two additional options that use URLSessionUploadTask instead of URLSessionDataTask.

// Upload data to url
Request.upload(data: data, to: "boards")

// Upload multipart data with parameters
// You are responsible for constructing a proper value,
// which is normally a string created from data.
Request.upload(
  multipartParameters: ["key": "value"],
  to: "http:/api.loc/posts"
)

Content types

query - creates a query string to be appended to any existing url.
formURLEncoded - uses application/x-www-form-urlencoded as a Content-Type and formats your parameters with percent-encoding.
json - sets the Content-Type to application/json and sends a JSON representation of the parameters as the body of the request.
multipartFormData - sends parameters encoded as multipart/form-data.
custom(String) - uses given Content-Type string as a header.

Encoding

Malibu comes with 3 parameter encoding implementations:

FormURLEncoder - a percent-escaped encoding following RFC 3986.
JsonEncoder - JSONSerialization based encoding.
MultipartFormEncoder - multipart data builder.

You can extend default functionality by adding a custom parameter encoder that conforms to ParameterEncoding protocol:

// Override default JSON encoder
Malibu.parameterEncoders[.json] = CustomJsonEncoder()

// Register encoder for the custom encoding type
Malibu.parameterEncoders[.custom("application/xml")] = CustomXMLEncoder()

Cache policy

URLSession handles cache based on the URLRequest.CachePolicy property:

let getRequest = Request.get("boards". cachePolicy: .useProtocolCachePolicy)

URLRequest.CachePolicy.useProtocolCachePolicy is the default policy for URL load requests. URLSession will automatically add the If-None-Match header in the request before sending it to the backend. When URLSession gets the 304 Not Modified response status it will call the URLSessionDataTask completion block with the 200 status code and data loaded from the cached response.

You can set cachePolicy property to .reloadIgnoringLocalCacheData if you want to prevent this automatic cache management. Then URLSession will not add the If-None-Match header to the client requests, and the server will always return a full response.

Networking

Networking class is a core component of Malibu that executes actual HTTP requests on a specified API service.

Initialization

It's pretty straightforward to create a new Networking instance:

// Simple networking that works with `SharkywatersEndpoint` requests.
let simpleNetworking = Networking<SharkywatersEndpoint>()

// More advanced networking
let networking = Networking<SharkywatersEndpoint>(
  // `OperationQueue` Mode
  mode: .async,
  // Optional mock provider
  mockProvider: customMockProvider,
  // `default`, `ephemeral`, `background` or `custom`
  sessionConfiguration: .default,
  // Custom `URLSessionDelegate` could set if needed
  sessionDelegate: self
)

Mode

Malibu uses OperationQueue to execute/cancel requests. It makes it easier to manage request lifetime and concurrency.

When you create a new networking instance there is an optional argument to specify mode which will be used:

sync
async
limited(maxConcurrentOperationCount)

Mocks

Mocking is great when it comes to writing your tests. But it also could speed up your development while the backend developers are working really hardly on API implementation.

In order to start mocking you have to do the following:

Create a mock provider

// Delay is optional, 0.0 by default.
let mockProvider = MockProvider(delay: 1.0) { endpoint in
  switch endpoint {
    case .fetchBoards:
      // With response data from a file:
      return Mock(fileName: "boards.json")
    case .showBoard(let id):
      // With response from JSON dictionary:
      return Mock(json: ["id": 1, "title": "Balsa Fish"])
    case .updateBoard(let id, let title):
      // `Data` mock:
      return Mock(
        // Needed response
        response: mockedResponse,
        // Response data
        data: responseData,
        // Custom error, `nil` by default
        error: customError
      )
    default:
      return nil
  }
}

Create a networking instance with your mock provider

Both real and fake requests can be used in a mix:

let networking = Networking<SharkywatersEndpoint>(mockProvider: mockProvider)

Session configuration

SessionConfiguration is a wrapper around URLSessionConfiguration and could represent 3 standard session types + 1 custom type:

default - configuration that uses the global singleton credential, cache and cookie storage objects.
ephemeral - configuration with no persistent disk storage for cookies, cache or credentials.
background - session configuration that can be used to perform networking operations on behalf of a suspended application, within certain constraints.
custom(URLSessionConfiguration) - if you're not satisfied with standard types, your custom URLSessionConfiguration goes here.

Pre-processing

// Use this closure to modify your `Request` value before `URLRequest`
// is created on base of it
networking.beforeEach = { request in
  return request.adding(
    parameters: ["userId": "12345"],
    headers: ["token": "eyJhbGciOiJIUzI1NiIsInR5cCI6IkpXVCJ9"]
  )
}

// Use this closure to modify generated `URLRequest` object
// before the request is made
networking.preProcessRequest = { (request: URLRequest) in
  var request = request
  request.addValue("eyJhbGciOiJIUzI1NiIsInR5cCI6IkpXVCJ9", forHTTPHeaderField: "token")
  return request
}

Middleware

Middleware is the function which works as the first promise in the chain, before the actual request. It could be used to prepare networking, do some kind of pre-processing task, cancel request under particular conditions, etc.

For example, in the combination with https://github.com/hyperoslo/OhMyAuth

// Set middleware in your configuration
// Remember to `resolve` or `reject` the promise
networking.middleware = { promise in
  AuthContainer.serviceNamed("service")?.accessToken { accessToken, error in
    if let error == error {
      promise.reject(error)
      return
    }

    guard let accessToken = accessToken else {
      promise.reject(CustomError())
      return
    }

    self.networking.authenticate(bearerToken: accessToken)
    promise.resolve()
  }
}

// Send your request like you usually do.
// Valid access token will be set to headers before the each request.
networking.request(request)
  .validate()
  .toJsonDictionary()

Authentication

// HTTP basic authentication with username and password
networking.authenticate(username: "malibu", password: "surfingparadise")

// OAuth 2.0 authentication with Bearer token
networking.authenticate(bearerToken: "eyJhbGciOiJIUzI1NiIsInR5cCI6IkpXVCJ9")

// Custom authorization header
networking.authenticate(authorizationHeader: "Malibu-Header")

Making a request

Networking is set up and ready, so it's time to fire some requests.

let networking = Networking<SharkywatersEndpoint>()

networking.request(.fetchBoards)
  .validate()
  .toJsonDictionary()
  .done({ data in
    print(data)
  })

networking.request(.createBoard(kind: 2, title: "Balsa Fish"))
  .validate()
  .toJsonDictionary()
  .done({ data in
    print(data)
  })

networking.request(.deleteBoard(id: 11))
  .fail({ error in
    print(error)
  })

Response and NetworkPromise

Response object consists of Data, URLRequest and HTTPURLResponse properties.

NetworkPromise is just a typealias to Promise, which is returned by every request method. You may use NetworkPromise object to add different callbacks and build chains of tasks. It has a range of useful helpers, such as validations and serialization.

let networkPromise = networking.request(.fetchBoards)

// Cancel the task
networkPromise.cancel()

// Create chains and add callbacks on promise object
networkPromise
  .validate()
  .toString()
  .then({ string in
    // ...
  })
  .done({ _ in
    // ...
  })

Offline storage

Want to store request when there is no network connection?

let request = Request.delete(
  "boards/1",
  storePolicy: .offline // Set store policy
)

Want to replay cached requests?

networking.replay().done({ result
  print(result)
})

Request storage is networking-specific, and while it replays cached requests it will be set to Sync mode. Cached request will go through normal request lifecycle, with applied middleware and pre-process operations. Request will be automatically removed from the storage when it's completed.

Backfoot surfer

Malibu has a shared networking object with default configurations for the case when you need just something simple to catch the wave. It's not necessary to create a custom RequestConvertible type, just call the same request method right on Malibu:

Malibu.request(Request.get("http://sharkywaters.com/api/boards")

Response

Serialization

Malibu gives you a bunch of methods to serialize response data:

let networkPromise = networking.request(.fetchBoards)

networkPromise.toData() // -> Promise
networkPromise.toString() // -> Promise
   
networkPromise.toJsonArray() // -> Promise<[[String: Any]]>
networkPromise.toJsonDictionary() // -> Promise<[String: Any]>

Validation

Malibu comes with 4 validation methods:

// Validates a status code to be within 200..<300
// Validates a response content type based on a request's "Accept" header
networking.request(.fetchBoards).validate()

// Validates a response content type
networking.request(.fetchBoards).validate(
  contentTypes: ["application/json; charset=utf-8"]
)

// Validates a status code
networking.request(.fetchBoards).validate(statusCodes: [200])

// Validates with custom validator conforming to `Validating` protocol
networking.request(.fetchBoards).validate(using: CustomValidator())

Logging

If you want to see some request, response and error info in the console, you get this for free. Just choose one of the available log levels:

none - logging is disabled, so your console is not littered with networking stuff.
error - prints only errors that occur during the request execution.
info - prints incoming request method + url, response status code and errors.
verbose - prints incoming request headers and parameters in addition to everything printed in the info level.

Optionally you can set your own loggers and adjust the logging to your needs:

// Custom logger that conforms to `ErrorLogging` protocol
Malibu.logger.errorLogger = CustomErrorLogger.self

// Custom logger that conforms to `RequestLogging` protocol
Malibu.logger.requestLogger = RequestLogger.self

// Custom logger that conforms to `ResponseLogging` protocol
Malibu.logger.responseLogger = ResponseLogger.self