Скачать или смотреть How to Update Struct Variable When Swiped in TabView Using SwiftUI?

Discover how to effectively manage state in SwiftUI's TabView by tracking the number of times a tab item is viewed. Learn to update a struct variable seamlessly!
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This video is based on the question https://stackoverflow.com/q/75282270/ asked by the user 'tryingtocode' ( https://stackoverflow.com/u/18338175/ ) and on the answer https://stackoverflow.com/a/75282689/ provided by the user 'vadian' ( https://stackoverflow.com/u/5044042/ ) at 'Stack Overflow' website. Thanks to these great users and Stackexchange community for their contributions.

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Update Struct Variable When Swiped in TabView

In iOS development with SwiftUI, developers often encounter the need to manage state in a dynamic and engaging way. One common scenario is tracking how many times a specific view or item has been displayed when users interact with your app. In this post, we will tackle the question: How do you update a struct variable when swiped in a TabView?

The Problem: Tracking Views in a TabView

Imagine you have a TabView that contains a series of items. You want to keep track of how many times each item has been viewed. The initial challenge arises from the use of Swift's struct, which is treated as a value type. This means that when you modify an instance of a struct, you're actually creating a copy rather than changing the original instance.

Example Scenario

Let's take a look at a simplified version of code that illustrates this problem:

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

What's Going Wrong?

The issue lies in the fact that modifying tempList[currentIndex] does not affect the original item in itemViewModel.list. Instead, it modifies a copy of the item because structs are value types in Swift. Therefore, the timesViewed variable does not get updated as intended.

The Solution: Modifying the Original Instance

To successfully update the timesViewed variable, you need to access and modify the original item in itemViewModel.list. Here’s a clearer way to achieve this:

Accessing the Item by ID

When the user swipes to a new tab, you can retrieve the original item from the list by using its ID. Here's how you can implement that:

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

Explanation of the Solution

Retrieve the ID: First, get the ID of the currently displayed item using tempList[value].id.

Find the Original Index: Use the firstIndex(where:) method to find the index of the original item in itemViewModel.list that matches this ID.

Update the Item: Finally, call the viewedThisItem() function on the original item using this index.

Important Note

Using force unwrapping with ! in this context is safe because you have ensured that the item does indeed exist in your list.

Conclusion

By understanding how value types work in Swift and using a method to modify the original instances, you can successfully implement functionality that tracks how many times an item in a TabView has been swiped and viewed. This approach not only enhances user experience but also gives you the ability to gather valuable user interaction data.

Integrating such features can greatly improve engagement and offer insights into how users are interacting with your application. Happy coding!