Hyperspace

Purpose

This library provides a simple abstraction around URLSession and HTTP. There are a few main goals:

• Wrap up all the HTTP boilerplate (method, headers, status codes, etc.) to allow your app to deal with them in a type-safe way.
• Provide a thin wrapper around URLSession:
  • Make error handling more pleasant.
  • Make it easy to define the details of your request and the model type you want to get back.
• Keep things simple.
  • There are currently around 800 SLOC, with about a quarter of that being boilerplate HTTP definitions.
  • Of course, complexity will increase over time as new features are added, but we're not trying to cover every possible networking use case here.

Key Concepts

• HTTP - Contains standard HTTP definitions and types. If you feel something is missing from here, please submit a pull request!
• Request - A protocol that defines the details of a request, including the desired result type. This is basically a thin wrapper around URLRequest, utilizing the definitions in HTTP.
• NetworkService - Uses a NetworkSession (URLSession by default) to execute URLRequests. Deals with raw HTTP and Data.
• BackendService - Uses a NetworkService to execute Requests. Transforms the raw Data returned from the NetworkService into the response model type defined by the Request. This is the main worker object your app will deal with directly.

Usage

1. Create Requests

You have two options to create requests - create your own struct or class that conforms to the Request protocol or by utilize the built-in AnyRequest<T> type-erased struct. Creating your own structs or classes is a bit more explicit, but can help encourage encapsulation and testability if your requests are complex. The AnyRequest<T> struct is generally fine to use for most cases.

Option 1 - Adopting the Request protocol

The CreatePostRequest in the example below represents a simple request to create a new post in something like a social network feed:

struct CreatePostRequest: Request {
    // Define the model we want to get back
    typealias ResponseType = Post
    typealias ErrorType = AnyError

    // Define Request property values
    var method: HTTP.Method = .post
    var url = URL(string: "http://jsonplaceholder.typicode.com/posts")!
    var headers: [HTTP.HeaderKey: HTTP.HeaderValue]? = [.contentType: .applicationJSON]
    var body: Data? {
        let encoder = JSONEncoder()
        return try? encoder.encode(newPost)
    }

    // Define any custom properties needed
    private let newPost: NewPost

    // Initializer
    init(newPost: NewPost) {
        self.newPost = newPost
    }
}

Option 2 - Using the AnyRequest<T> struct

let createPostRequest = AnyRequest<Post>(method: .post,
                                         url: URL(string: "http://jsonplaceholder.typicode.com/posts")!,
                                         headers: [.contentType: .applicationJSON],
                                         body: postBody)

For the above examples, the Post response type and NewPost body are defined as follows:

struct Post: Decodable {
    let id: Int
    let userId: Int
    let title: String
    let body: String
}

struct NewPost: Encodable {
    let userId: Int
    let title: String
    let body: String
}

2. Create Request defaults (optional)

To avoid having to define default Request property values for every request in your app, it can be useful to extend Request with the defaults you want every request to have:

extension Request {
    var cachePolicy: URLRequest.CachePolicy {
        return .reloadIgnoringLocalCacheData
    }

    var timeout: TimeInterval {
        return 60.0
    }
}

Alternatively, you can also modify the values of RequestDefaults directly:

RequestDefaults.defaultTimeout = 60 // Default timeout is 30 seconds
RequestDefaults.defaultCachePolicy = .reloadIgnoringLocalCacheData // Default cache policy is '.useProtocolCachePolicy'

3. Create a BackendService to execute your requests

We recommend adhering to the Interface Segregation principle by creating separate "controller" objects for each section of the API you're communicating with. Each controller should expose a set of related funtions and use a BackendService to execute requests. However, for this simple example, we'll just use BackendService directly as a private property on the view controller:

class ViewController: UIViewController {

    private let backendService = BackendService()

    // Rest of your view controller code...
}

4. Instantiate your Request

Let's say our view controller is supposed to create the post whenever the user taps the "send" button. Here's what that might look like:

@IBAction private func sendButtonTapped(_ sender: UIButton) {
    let title = ... // Get the title from a text view in the UI...
    let message = ... // Get the message from a text view/field in the UI...
    let post = NewPost(userId: 1, title: title, body: message)

    let createPostRequest = CreatePostRequest(newPost: post)

    // Execute the network request...
}

5. Execute the Request using the BackendService

For the above example, here's how you would execute the request and parse the response. While all data transformation happens on the background queue that the underlying URLSession is using, all BackendService completion callbacks happen on the main queue so there's no need to worry about threading before you update UI. Notice that the type of the success response's associated value below is a Post struct as defined in the CreatePostRequest above:

backendService.execute(request: createPostRequest) { [weak self] result in
    debugPrint("Create post result: \(result)")

    switch result {
    case .success(let post):
        // Insert the new post into the UI...
    case .failure(let error):
        // Alert the user to the error...
    }
}

Example

To run the example project, you'll first need to use Carthage to install Hyperspace's dependencies (Result and SwiftLint).

After installing Carthage, clone the repo:

git clone https://github.com/BottleRocketStudios/iOS-Hyperspace.git

Next, use Carthage to install the dependencies:

carthage update

From here, you can open up Hyperspace.xcworkspace and run the examples:

Shared Code

• Models.swift, Requests.swift
  • Sample models and network requests shared by the various examples.

Example Targets

• Hyperspace-iOSExample
  • ViewController.swift
    • View a simplified example of how you might use this in your iOS app.
• Hyperspace-tvOSExample
  • ViewController.swift
    • View a simplified example of how you might use this in your tvOS app (this is essentially the same as the iOS example).
• Hyperspace-watchOSExample Extension
  • InterfaceController.swift
    • View a simplified example of how you might use this in your watchOS app.

Playgrounds

• Playground/Hyperspace.playground
  • View and run a single file that defines models, network requests, and executes the requests similar to the example targets above.
• Playground/Hyperspace_AnyRequest.playground
  • The same example as above, but using the AnyRequest<T> struct.
• Playground/Hyperspace_DELETE.playground
  • An example of how to deal with requests that don't return a result. This is usually common for DELETE requests.

Requirements

• iOS 8.0+
• tvOS 9.0+
• watchOS 2.0+
• Swift 5.0

Installation

Hyperspace is available through CocoaPods. To install it, simply add the following line to your Podfile:

pod 'Hyperspace'

Author

Bottle Rocket Studios

License

Hyperspace is available under the Apache 2.0 license. See the LICENSE.txt file for more info.