The $(.) syntax is called variable substitution. Note how the values aren’t set to any sort of valid ID, but instead set to $(TRANSPORT_API_SERVICE_APP_ID) and $(TRANSPORT_API_SERVICE_APP_KEY). These values are loaded from the app’s ist, specifically from the TRANSPORT_API_SERVICE_APP_ID and TRANSPORT_API_SERVICE_APP_KEY keys, respectively. The important part to note in this class is appId and appKey on lines 82 and 83.
This class handles fetching the JSON data from a network request in fetchStatus() and decodes the JSON into the AllLinesStatus struct. Open TransportAPIService.swift in the API group. As this is a published object, SwiftUI handles updating the UI automatically. Once fetched, tubeStatusState is updated. This handles fetching the data from the API. By passing the fetchCurrentStatus enum as the action, this method calls fetchCurrentStatus().įetchCurrentStatus() calls fetchStatus() on an instance variable of type conforming to the TubeLinesStatusFetcher protocol. You’ve already seen how TubeStatusView calls perform(action:) when it appears on the screen. The important parts of this class are marked under Actions and Action Handlers. You can look at the SwiftUI previews to see what these rows will look like. This is a simple view that displays the status of a particular Tube line. Open LineStatusRow.swift and have a quick look around. This method asks the model to perform fetchCurrentStatus by calling perform(action:). This calls loadData() of the view when it first appears on the screen. Notice how the view also contains onAppear(perform:). It also displays Text showing when the data was last updated. Once data loading completes, TubeStatusView shows LineStatusRow for each line.
The body of the view displays a ZStack that sets the background color of the view and then displays a Loadable on top. TubeStatusView observes a model object of type TubeStatusViewModel.
The main view displays a view called TubeStatusView, which acts as the root view of the app. Note: If you aren’t interested in learning about the inner workings of the app, you can skip ahead to Setting up TransportAPI. This is what you’ll do now after going through a walk-through of how the app works. Uh oh! It errors! This is because you need to set up the app to fetch data for the tube lines. This way, users can get the information they need with a glance. You’ll add to the project by associating an SF Symbol with each status and having it display in the app. The app displays the current status of Tube lines.
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Create your own, custom symbols for use in your app.įirst, download the project materials using the Download Materials button at the top or bottom of this tutorial and open the starter project in Xcode.Associate different SF Symbols with different statuses.Here, you’ll add new bling icons to an app showing the status of London Underground train lines, commonly known as the Tube. And, if you can’t find exactly what you need, you can create it. With so many ready-made options, you’re likely to find the perfect fit for your app’s style. They provide an easy way to add iconography to your projects, as they come in a wide variety of sizes and weights. They’re designed to work well with the default system font on Apple devices called San Francisco. SF Symbols are a set of over 2,400 symbols, or icons, curated by Apple.
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In this tutorial, you’ll learn all about SF Symbols as well as how to create your own custom symbols to help your app stand out from the crowd! :]
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