Скачать или смотреть How to Add Test Data to PreviewProvider in SwiftUI

Learn how to easily inject `test data` into your SwiftUI PreviewProvider while using MVVM architecture. This guide offers step-by-step instructions for newcomers to iOS and Swift development.
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This video is based on the question https://stackoverflow.com/q/63997052/ asked by the user 'Rubaninferno' ( https://stackoverflow.com/u/11717309/ ) and on the answer https://stackoverflow.com/a/63997127/ provided by the user 'pawello2222' ( https://stackoverflow.com/u/8697793/ ) at 'Stack Overflow' website. Thanks to these great users and Stackexchange community for their contributions.

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How to Add Test Data to PreviewProvider in SwiftUI

As a newcomer to iOS and Swift development, especially when using the MVVM architecture, you might find yourself needing to test your UI quickly and effectively. One common question that arises is how to send in test data to the SwiftUI Preview. This post will guide you through the steps necessary to accomplish this.

Understanding the Need for Test Data

In software development, especially when working with user interfaces, it's essential to visualize how the UI will behave with different sets of data. Often, data comes from an API call, but for preview purposes, developers utilize mock or test data. This allows you to design and validate UI elements without needing to wait for asynchronous data fetching.

Example Test Data

For this example, we are using the following test data:

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Structure Overview

Before we dive into implementing our test data, let’s briefly look at the components we’ll be working with:

TodayView - This is the main view that displays a list of items.

ViewModel - This handles the data logic and communicates with APIs.

Model - This defines the structure of the data we are working with.

Step-by-Step Guide to Add Test Data

1. Modifying the ViewModel

In your ViewModel, remove the loadData() call from the init method. This step is crucial, as including this call would override any test data you set up.

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2. Assigning Test Data in the PreviewProvider

Next, you'll need to inject this test data into the TodayView_Previews. Here’s how you can do that:

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3. Use the Test Data in the View

With the above steps, when you run the preview for TodayView, it will now display the data from testData rather than waiting for an API call. This makes it much easier to design and test UI components.

Conclusion

Adding test data to your SwiftUI PreviewProvider is a straightforward process that greatly enhances your development experience. You can verify your UI's appearance and functionality quickly without relying on external data sources.

Utilizing the strategy outlined in this post will allow you to mock data for any other components you may build in SwiftUI, helping you to become more proficient in iOS app development.

If you have any questions or need further assistance, feel free to reach out in the comments below or explore additional resources related to SwiftUI and MVVM.