Скачать или смотреть Solving SwiftUI Date Persistence Issues in View Navigation

Learn how to resolve issues with date parameters in SwiftUI views that do not persist correctly across navigations.
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Solving SwiftUI Date Persistence Issues in View Navigation

If you're developing an app using SwiftUI, you might encounter a common issue where a date parameter does not persist correctly when navigating between views. This can be particularly troublesome when you're relying on UserDefaults to store and retrieve values such as dates. In this guide, we will explore how to properly manage date values in SwiftUI so that they remain consistent across multiple view navigations without having to restart the app.

The Problem

In the scenario described, when the user navigates to a view called PayScheduleForm, the date value is correctly loaded from UserDefaults the first time. However, after the user changes this value and navigates back to the SettingsView, upon returning to PayScheduleForm, the original date still appears. This indicates that the updated date hasn’t been retrieved from UserDefaults again.

Step-by-Step Breakdown of the Issue:

Start the App: The application loads PayScheduleForm for the first time.

Navigate to Pay Schedule: The last saved date is displayed correctly.

Update the Date: The user changes the date to a new value and it updates UserDefaults.

Go Back to Settings: The user navigates back using the back button.

Return to Pay Schedule: The original date value reappears, instead of the updated one.

Restarting the App: The last change is reflected only after the app is restarted.

The Solution

To address this issue, we can leverage the @ ObservableObject protocol in SwiftUI, which allows views to respond to changes in data automatically. Starting with iOS 14, the @ AppStorage property wrapper is introduced for quick access to UserDefaults, but it’s limited in that it does not support certain types, such as Date. However, using an ObservableObject provides an elegant workaround.

Steps to Implement the Solution

Create an Observable Object: First, we will need to scavenge through the UserDefaults and make the date a part of an ObservableObject. We will create a UserSettings class to manage the date.

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In this class:

The date property is marked with @ Published, meaning any changes to it will notify the views observing this object to refresh.

The didSet property observer updates UserDefaults when the date changes.

The init method attempts to load the existing date from UserDefaults or sets a default date.

Update your Views: Next, incorporate this UserSettings object into your SettingsView and PayScheduleForm views:

[[See Video to Reveal this Text or Code Snippet]]

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By declaring @ EnvironmentObject, the PayScheduleForm can access the same UserSettings instance managed by SettingsView, ensuring that the updated date value persistently reflects across navigations.

Conclusion

By adopting this approach, you can seamlessly maintain the state of date values in your SwiftUI app, avoiding the frustrating scenario of reloading outdated parameters. Using ObservableObject, along with @ Published properties, enables you to create dynamic views that respond to changes effortlessly. Now, the next time you find yourself deep into SwiftUI development and facing similar problems, you will have a solid solution ready to implement.

With these improvements, your application will provide a more reliable and user-friendly experience when dealing with date selections. Happy Coding!