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Asynchronous Programming with SwiftUI and Combine: Functional Programming to Build UIs on Apple Platforms

by Peter Friese

January 2023

Intermediate to advanced

447 pages

6h 44m

English

Apress

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Who Should Read This BookHow This Book Is OrganizedAbout the Code
Why a New UI Framework?SwiftUI PrinciplesDeclarative vs. ImperativeState ManagementComposition over InheritanceEverything Is a View—Except That It Isn’tUIs Are a Function of Their StateA Quick Tour of SwiftUIPrerequisitesCreating a New SwiftUI AppAdding Some Interaction to Your AppUsing SwiftUI’s State Management to Keep UI and Model in SyncExercisesSummary
What We’re Going to BuildComposing a View for Displaying a BookBuild the View with Static DataUsing the Preview to Make Sure Our View Works As IntendedDisplaying a List of BooksSetting Up Data BindingAdjusting the Preview CanvasMaking the Code ReusableRefactoring the Code Using Extract SubviewRenaming ContentViewKeep Complexity in CheckViews and View ModifiersExercisesTips and TricksSummary

ViewsUser Interface ViewsText Input and OutputImagesControls and IndicatorsShapesContainer ViewsLayout BehaviorHuggingExpandingViews Are Just Descriptions of the UIView ModifiersConfiguring ViewsApplying View Modifiers to Child ViewsUsing View Modifiers to Register Action HandlersSummary
Managing State in SwiftUIBinding Value TypesBinding ObjectsObservableObject@StateObjectWhen to Use@ObservedObjectWhen to Use@EnvironmentObjectWhen to UseSummary
Getting Started with Lists in SwiftUIUsing Other SwiftUI Views Inside List RowsBuilding Custom List RowsMore Complex List RowsDynamic ListsDisplaying a List of ElementsUsing List Bindings to Allow Modifying List ItemsAsynchronously Fetching DataPull-to-RefreshSearchingStylingList StylesHeaders and FootersList CellsSeparatorsActionsSwipe-to-DeleteMoving and Deleting Items Using EditModeSwipe ActionsBasic Swipe ActionsSpecifying the EdgeSwipe Actions and onDeleteAdding More Swipe ActionsFull SwipeStyling Your Swipe ActionsManaging Focus in ListsHow to Manage Focus in SwiftUIHow to Manage Focus in ListsHandling the Enter KeyWhat About MVVM?Eliminating Empty ElementsSummary
Building Simple FormsShowing Data in a FormMake It EditableDrill-Down NavigationInput ValidationUsing .onChange(of:)Using a View Model to Handle Form ValidationSynchronizing a Local Source of Truth with the Global Source of Truth by Using @Binding and @ObservableObjectUsing Combine to Perform Form ValidationSummary
What Is Functional Reactive Programming?PublishersSubscribersOperatorsComposing OperatorsCombining PublishersSummary
Input Validation Using CombineThe Sign-Up Form ViewThe View ModelValidating the UsernameDisplaying Validation MessagesEncapsulating Combine Pipelines in Computed PropertiesValidating the PasswordPutting It All TogetherExercises5Summary
Fetching Data Using URLSessionUsing Combine to Fetch DataDestructuring Tuples Using Key PathsMapping DataFetching Data Using Combine, SimplifiedConnecting to the UIHandling MultithreadingOptimizing Network AccessFinding the Root CauseUsing the share Operator to Share a PublisherUsing debounce to Further Optimize the UXUsing removeDuplicates to Avoid Sending the Same Request TwiceBringing It All TogetherExercisesSummary
Error Handling StrategiesIgnoring the ErrorRetrying (with Exponential Backoff)Showing an Error MessageReplacing the Entire View with an Error ViewShowing an Inline Error MessageTypical Error Conditions and How to Handle ThemImplementing a Fallible Network APICalling the API and Handling ErrorsHandling Device/Network Offline ErrorsHandling Validation ErrorsHandling Response Parsing ErrorsHandling Internal Server ErrorsSummary
What Is a Combine Operator?Implementing Custom OperatorsImplementing a Retry Operator with a DelayConditionally RetryingImplementing a Retry Operator for Exponential BackoffSummary
A Case StudyUsing Combine to Access FirestoreUsing View Models and Published PropertiesUsing Combine to Wrap APIsCreating Your Own PublishersUsing PassthroughSubject to Wrap Snapshot ListenersUsing Future to Implement One-Time Fetching from FirestoreSummary
What Is a SchedulerTypes of SchedulersDefault BehaviorSwitching SchedulersControlling Upstream Publishers Using subscribe(on:)Controlling Downstream Subscribers Using receive(on:)Other Operators That Influence SchedulingPerforming Asynchronous WorkIntegrating with Other APIsURLSessionFirebaseSummary
Synchronous Programming with FunctionsAsynchronous Programming with ClosuresAsynchronous Programming with async/awaitDefining and Calling Asynchronous FunctionsCalling Asynchronous Functions in ParallelSummary
Fetching Data Asynchronously Using URLSessionCalling Asynchronous CodeThe Task View ModifierCalling Asynchronous Code When the User Taps a ButtonUsing Pull-to-Refresh to Update Views AsynchronouslySearchable Views and async/awaitUpdating the UI from the Main ThreadSummary
Fetching Data Using CombineFetching Data Using async/awaitIs This the End of Combine?Connecting the UI……to a Combine Pipeline…to an async/await MethodCalling Asynchronous Code from CombineSummary

Content preview from Asynchronous Programming with SwiftUI and Combine: Functional Programming to Build UIs on Apple Platforms

P. FrieseAsynchronous Programming with SwiftUI and Combinehttps://doi.org/10.1007/978-1-4842-8572-5_16

16. Bringing It All Together: SwiftUI, async/await, and Combine

Peter Friese¹

(1)

Hamburg, Germany

Mobile applications have to deal with a constant flow of events: user input, network traffic, and callbacks from the operating system are all vying for your app’s attention. Building apps that feel snappy is a challenging task, as you have to efficiently handle all those events.

Combine and async/await are some fairly recent addition to the collection of frameworks and language features that aim at making this easier.

In this chapter, we will explore commonalities ...