Netable

2.1.0

A Swift library for encapsulating network APIs using Codable in a type-oriented way.
steamclock/netable

What's New

v2.1.0 - Partial Array Decoding

2022-12-14T18:29:42Z

Added support for partially decoding arrays through new arrayDecodingStrategy parameter on Request.
Fixed RetryConfiguration not being marked as Sendable.

Swift Package Manager compatiblePRs WelcomeLicense: MIT Platform

Modern apps interact with a lot of different APIs. Netable makes that easier by providing a simple interface for using those APIs to drive high quality iOS and MacOS apps, built on Swift Codable, while still supporting non-standard and unusual APIs when need be.

Features

Netable is built on a number of core principles we believe a networking library should follow:

  • Handle the simplest REST API calls with minimal code, while still having the extensibility to decode the gnarliest responses
  • Leverage Swift’s Codabale protocols for automatic decoding and encoding
  • Avoid monolithic networking files and avoid wrappers
  • Straightforward global and local error handling
  • Add a little bit of magic, but only where it goes a long way

Usage

Standard Usage

Make a new instance of Netable, and pass in your base URL:

let netable = Netable(baseURL: URL(string: "https://api.thecatapi.com/v1/")!)

Extend Request

struct CatImage: Decodable {
    let id: String
    let url: String
}

struct GetCatImages: Request {
    typealias Parameters = [String: String]
    typealias RawResource = [CatImage]

    public var method: HTTPMethod { return .get }

    public var path: String {
        return "images/search"
    }

    public var parameters: [String: String] {
        return ["mime_type": "jpg,png", "limit": "2"]
    }
}

Make your request using async/await and handle the result:

Task {
    do {
        let catImages = try await netable.request(GetCatImages())
        if let firstCat = catImages.first,
           let url = URL(string: firstCat.url),
           let imageData = try? Data(contentsOf: url) {
            self.catsImageView1.image = UIImage(data: imageData)
        }

        if let lastCat = catImages.last,
           let url = URL(string: lastCat.url),
           let imageData = try? Data(contentsOf: url) {
            self.catsImageView2.image = UIImage(data: imageData)
        }
    } catch {
        let alert = UIAlertController(
            title: "Uh oh!",
            message: "Get cats request failed with error: \(error)",
            preferredStyle: .alert
        )

        alert.addAction(UIAlertAction(title: "OK", style: .cancel))
        self.present(alert, animated: true, completion: nil)
    }
}

Making a request with Combine

netable.request(GetCatImages())
    .sink { result in
        switch result {
        case .success(let catImages):
            if let firstCat = catImages.first,
               let url = URL(string: firstCat.url),
               let imageData = try? Data(contentsOf: url) {
                self.catsImageView1.image = UIImage(data: imageData)
            }

            if let lastCat = catImages.last,
               let url = URL(string: lastCat.url),
               let imageData = try? Data(contentsOf: url) {
                self.catsImageView2.image = UIImage(data: imageData)
            }
        case .failure(let error):
            let alert = UIAlertController(
                title: "Uh oh!",
                message: "Get cats request failed with error: \(error)",
                preferredStyle: .alert
            )

            alert.addAction(UIAlertAction(title: "OK", style: .cancel))
            self.present(alert, animated: true, completion: nil)
        }
    }.store(in: &cancellables)

Or, if you prefer good old fashioned callbacks

netable.request(GetCatImages()) { result in
    switch result {
    case .success(let catImages):
        if let firstCat = catImages.first,
           let url = URL(string: firstCat.url),
           let imageData = try? Data(contentsOf: url) {
            self.catsImageView1.image = UIImage(data: imageData)
        }

        if let lastCat = catImages.last,
           let url = URL(string: lastCat.url),
           let imageData = try? Data(contentsOf: url) {
            self.catsImageView2.image = UIImage(data: imageData)
        }
    case .failure(let error):
        let alert = UIAlertController(
            title: "Uh oh!",
            message: "Get cats request failed with error: \(error)",
            preferredStyle: .alert
        )

        alert.addAction(UIAlertAction(title: "OK", style: .cancel))
        self.present(alert, animated: true, completion: nil)
    }
}

Resource Extraction

Have your request object handle extracting a usable object from the raw resource

struct CatImage: Decodable {
    let id: String
    let url: String
}

struct GetCatImageURL: Request {
    typealias Parameters = [String: String]
    typealias RawResource = [CatImage]
    typealias FinalResource = URL

     // ...

    func finalize(raw: RawResource) async throws -> FinalResource {
        guard let catImage = raw.first else {
            throw NetableError.resourceExtractionError("The CatImage array is empty")
        }

        guard let url = URL(string: catImage.url) else {
            throw NetableError.resourceExtractionError("Could not build URL from CatImage url string")
        }

        return url
    }
}

Leave your network code to deal with the important stuff

Task { 
    do {
        let catUrl = try await netable.request(GetCatImages())
        guard let imageData = try? Data(contentsOf: catUrl) else {
            throw NetableError.noData
        }

        self.imageView.image = UIImage(data: imageData)
    } catch {
        // ...
    }
}

Smart Unwrapping Objects

Sometimes APIs like to return the object you actually care about inside of a single level wrapper, which Finalize is great at dealing with, but requires a little more boilerplate code than we'd like. This is where SmartUnwrap<> comes in!

Create your request as normal, but set your RawResource = SmartUnwrap<ObjectYouCareAbout> and FinalResource = ObjectYourCareAbout. You can also specify Request.smartUnwrapKey to avoid ambiguity when unwrapping objects from your response.

Before:

struct UserResponse {
    let user: User
}

struct User {
    let name: String
    let email: String
}

struct GetUserRequest: Request {
    typealias Parameters: GetUserParams
    typealias RawResource: UserResponse
    typealias FinalResource: User
    
    // ...
    
    func finalize(raw: RawResource) async throws -> FinalResource {
        return raw.user
    }
}

After:

struct User: {
    let name: String
    let email: String
}

struct GetUserRequest: Request {
    typealias Parameters: GetUserParams
    typealias RawResource: SmartUnwrap<User>
    typealias FinalResource: User
}

Partially Decoding Arrays

Sometimes, when decoding an array of objects, you may not want to fail the entire request if some of those objects fail to decode.

To do this, you can set your Request's arrayDecodeStrategy to .lossy to return any elements that succeed to decode.

Not that this will only work if your RawResource: Sequence or RawResource: SmartUnwrap<Sequence>. For better support of decoding nested, lossy, arrays we recommend checking out Better Codable

Handling Errors

In addition to handling errors locally that are thrown, or returned through Result objects, we provide two ways to handle errors globally. These can be useful for doing things like presenting errors in the UI for common error cases across multiple requests, or catching things like failed authentication requests to clear a stored user.

Using requestFailureDelegate

See GlobalRequestFailureDelegate in the Example project for a more detailed example.

extension GlobalRequestFailureDelegateExample: RequestFailureDelegate {
    func requestDidFail<T>(_ request: T, error: NetableError) where T : Request {
        let alert = UIAlertController(title: "Uh oh!", message: error.errorDescription, preferredStyle: .alert)
        present(alert, animated: true)
    }
}

Using requestFailurePublisher

If you prefer Combine, you can subscribe to this publisher to receive NetableErrors from elsewhere in your app.

See GlobalRequestFailurePublisher in the Example project for a more detailed example.

netable.requestFailurePublisher.sink { error in
    let alert = UIAlertController(title: "Uh oh!", message: error.errorDescription, preferredStyle: .alert)
    self.present(alert, animated: true)
}.store(in: &cancellables)

Using FallbackResource

Sometimes, you may want to specify a backup type to try and decode your response to if the initial decoding fails, for example:

  • You want to provide a fallback option for an important request that may have changed due to protocol versioning
  • An API may send back different types of responses for different types of success

Request allows you to optionally declare a FallbackResource: Decodable associated type when creating your request. If you do and your request fails to decode the RawResource, it will try to decode your fallback resource, and if successful, throw a NetableError.fallbackDecode with your successful decoding.

See FallbackDecoderViewController in the Example project for a more detailed example.

GraphQL Support

While you can technically use Netable to manage GraphQL queries right out of the box, we've added a helper protocol to make your life a little bit easier, called GraphQLRequest.

You can see a detailed example in the example project, but note that by default it's important that your .graphql file's name matches exactly with your request.

We recommend using a tool like Postman to document and test your queries. Also note that currently, shared fragments are not supported.

Example

Full Documentation

In-depth documentation is provided through Jazzy and GitHub Pages.

Installation

Requirements

  • iOS 15.0+
  • MacOS 10.15+
  • Xcode 11.0+

Netable is available through Swift Package Manager. To install it, follow these steps:

  1. In Xcode, click File, then Swift Package Manager, then Add Package Dependency
  2. Choose your project
  3. Enter this URL in the search bar https://github.com/steamclock/netable.git

Supporting earlier version of iOS

Since Netable 2.0 leverages async/await under the hood, if you want to build for iOS versions before 15.0 you'll need to use v1.0.

License

Netable is available under the MIT license. See the License.md for more info.

Description

  • Swift Tools 5.1.0
View More Packages from this Author

Dependencies

  • None
Last updated: Wed Feb 08 2023 16:15:43 GMT-0500 (GMT-05:00)