Type-safe network calls made easy

Netswift offers an easy way to perform network calls in a structured and type-safe way.

Networking in Swift can be tedious from the get go. Type safety & reusability are often overlooked for the sake of getting up to speed. Have a huge file with all your API calls which is getting hard to maintain? This is where Netswift comes in.

This is how easy it is to perform network calls with Netswift:

Netswift().peform(StripeAPI.Charges.get(byID: "1234")) { result in
  switch result {
  case .failure(let error):
    // Our request failed: we can use the error to debug it
    print(error)
    
  case .success(let charge):
    // Our request succeeded: we now have a Charge object from the Stripe API
    print(charge.amount)
  }
}

I'm assuming you have an available iOS project set up with this cocoapod, ready to go. If not, please follow the installation steps.

As all reputable tutorials, the following steps will help you set up our first Hello World request.

• Step 1: Define a container which will act as the base of implementation for our API.
• Step 2: Implement NetswiftRoute, which defines the different URLComponents of our endpoints.
• Step 3: Implement NetswiftRequest, which defines how your container can be turned into a URLRequest
• Step 4: Passing it all to the generic Netswift class and performing your first request 🙌
• Step 5: ????
• Step 6: Profit 👍

To facilitate this tutorial, I went ahead and set up a mock API for you to query. It only has one endpoint, which returns a single object that contains a title. Give it a try

In this particular case, and to keep things simple, we can go ahead and define a new enum. We'll use it to implement the minimum required protocol functions which will allow us to perform our request.

So go ahead; add a new file to your project and name it however you like. I chose MyAPI. Then, don't forget to import Netswift, and create your API Container like such:

import Netswift

enum MyAPI {
  case helloWorld
}

And that's pretty much it. Now, since our API only has one endpoint, there's really nothing more to this. The great thing about Swift's enum is that they can also have associated values. This comes in very handy when you need to pass additional data to your endpoint, all while keeping it type-safe & structured. Neat 👌

So we have our enum. Great. But it doesn't do much. Let's fix that.

Go ahead and define an extension for it which implements the NetswiftRoute protocol:

extension MyAPI: NetswiftRoute {
}

Immediately, the compiler starts complaining. Pressing 'Add protocol stubs' will make it happy again. This will add two variables:

• host: This defines the domain of our API, usually something like www.example.com.
• path: A specific resource on our API. Unless you're just GET-ing a website, you'll need to define a path.

So let's go ahead and implement those two.

var host: String {
  return "my-json-server.typicode.com"
}

var path: String? {
  switch self {
    case .helloWorld: return "MrSkwiggs/Netswift-HelloWorld/Netswift"
  }
}

What did we just do ?

Our container is an enum, which means we can very easily define different return values given each case. For the host, we always want to return the same value.

For the path however, we are taking advantage of this feature. We set it up in a future-proof way so that we can always add paths later (as new enum cases). When that time comes, the compiler will yell at us for not covering all cases of our enum 👍

And that's pretty much everything we need for now. A lot of work is done under the hood by default; we can always define more information such as scheme (http or https) and query it if we need it, but in the context of this tutorial we can just skip ahead!

Now that we have our route setup, all we need to do is implement the NetswiftRequest protocol. Let us do just that in another extension:

extension MyAPI: NetswiftRequest {
}

This time, we don't want to let the compiler add protocol stubs for us just yet. Before we do that, let me explain what other information we need to provide to Netswift;

• A Response type. Since Netswift is generic, it doesn't know what kind of data we want from our API's endpoint. If our request defines a type called Response, we're good to go. And the best part is, we could also use a typealias, and it would just work 👍

So for now, let's just add an internal type named Response in our extension:

struct Response: Decodable {
  let title: String
}

Again, what did we just write?

Well, first of all, we define a type that mimics our endpoint's response structure. That is, an object that contains a member named title, which is of type String.

Then, we told the compiler that our Response type implements the Decodable protocol. Netswift, uses Swift's generic JSONDecoder. This is all done behind the scenes by default implementations.

Yet, the compiler is still unhappy. Now's however a good time to let it 'Add protocol stubs'. We're now given a new function called serialise. This is the last part we need to define before we are good to go.

So let us implement our URLRequest serialisation then, shall we ?

func serialise(_ handler: @escaping NetswiftHandler<URLRequest>) {
  handler(.success(URLRequest(url: self.url)))
}

Alright what's all that, now ? Well, the serialise function lets Netswift get a useable URLRequest that it can send out. Since our implementation is so basic, though, all we need to do is instantiate a URLRequest with a given URL. But wait. Where's self.url coming from ?

This convenience computed variable comes from the NetswiftRoute protocol. All it does is to simply format all the URLComponents you've defined into a String, which it then uses to instantiate & return a URL object.

Again, a lot of default implementation there, but all you need to know is that, for our current .helloWorld case, self.url will be using <scheme><host>/<path><query>.

Great, that's us pretty much done now!

Now's the moment we've been waiting for: sending out our request!

All we need to do is to actually perform our request. To do so, we can use an instance of the default Netswift class. All we need to do is call this:

Netswift().perform(MyAPI.helloWorld) { result in
  switch result {
  case .failure(let error):
    // Our request failed: we can use the error to debug it
    print(error)
    
  case .success(let value):
    // Our request succeeded: we now have an object of type MyAPI.Response available to use
    print(value.title)
  }
}

And that's our first request done with Netswift! From here, you can take it further and start defining more complex requests. I'd also suggest reading up the documentation and overriding default implementations to see what this library can really achieve 👌

To run the example project, clone the repo, and run pod install from the Example directory first. It contains the full implementation of the tutorial above, along a few other examples.

Netswift is available through:

• CocoaPods: To install it, simply add the following line to your Podfile

pod 'Netswift'

• Swift Package Manager: To install it, simply search for it through XCode's integrated package navigator

Dorian Grolaux, https://skwiggs.dev

Netswift is available under the MIT license. See the LICENSE file for more info.