RxSwift Xcode file templates

A handful of Xcode file templates for projects that use RxSwift and my own variation of MVVM

What this is about:

These file templates are meant to be used for the following app architecture setup:

Let's call each "screen" or "view" in the app a Scene. So if you have an app that has a list view, a detail view and a login view you have 3 Scenes.

Each Scene consists of the following elements:

ViewController

✅ Does

• initialize and layout its subviews
• handle user input (if data needs to be fetched or stored it relays that to the ViewModel)
• show Displayable Items that are provided by the ViewModel

❌ Does Not

• have any access to API, DataStore, UserDefaults
• push other ViewControllers or pop itself
• present other ViewControllers modally
• show Alerts
• format Data to be displayable in Views (e.g. AttributedStrings, DateFormatters)

---

ViewModel

✅ Does

• fetch data from API
• fetch / store / update Data from DataStore
• fetch / store / update Data from UserDefaults
• format Data to be displayable by the ViewController (e.g. Attributed Strings, DateFormatters)

❌ Does Not

• have any access to UIElements (does not even import UIKit!)

---

Router

✅ Does

• push other Scenes (if they are should be on the same navigaton stack)
• generate a RouteRequest for Scenes that should be presented by the main AppRouter

❌ Does Not

• have any access to UIElements (does not even import UIKit!)
• have any access to API, DataStore, UserDefaults

---

Builder

✅ Does

• initialize ViewController, ViewModel and Router
• provide the ViewController to the outside world (via the viewController() method)
• if the Scene needs some initial data it is injected into the Builder who then injects it into the ViewModel

❌ Does Not

• do anything else ;-)

---

Initializing a new scene

When you want to show a new scene you never initialize any of its components yourself. Always ask the Scene's Builder to provide the Scene's ViewController via its static viewController() method:

let nextViewController = NextBuilder.viewController()

If the new Scene needs some initial data you inject it into the new Scene's Builder.

A simple example:
You have a CarListScene that shows a list of cars. When the user taps on a car in the list you want to navigate to a CarDetailsScene that shows the details of the selected car. To hand the carID to the Details Scene you inject it into the CarDetailsBuilder:

class CarListRouter {
    weak var viewController: CarListViewController?

    func navigateToDetails(withCarID carID: String) {
        let detailsViewController = CarDetailsBuilder.viewController(withCarID: carID)
        viewController?.navigationController?.pushViewController(detailsViewController, animated: true)
    }
}

The CarDetailsBuilder then injects the data into the CarDetailsViewModel:

struct CarDetailsBuilder {

    static func viewController(withCarID carID: String) -> UIViewController {
        let viewModel = CarDetailsViewModel(withCarID: carID)
        let router = CarDetailsRouter()
        let viewController = CarDetailsViewController(withViewModel: viewModel, router: router)
        router.viewController = viewController

        return viewController
    }
}

And then the CarDetailsViewModel prepares displayable data for the CarDetailsViewController as it always does.

How to use the Xcode templates:

1. Download the RxSwift folder and add it to the following folder on your machine: ~/Library/Developer/Xcode/Templates (You might need to create that folder if does not exist yet)

2. When you want to add a new scene to your app, open the New File dialog and choose RxSwift in the left column

3. Select Scene and click Next

4. Enter a name for the Scene. As you can see that name will be used as a prefix for all the 4 classes that will be needed for the scene (see above)

5. Click Next and save the scene. Xcode now creates the 4 classes needed for the scene.

Requirements

• Xcode 9 (for prior versions use 0.4.0)
• Swift 4