How to Properly Initialize a View by Observing @ StateObject in SwiftUI

Learn how to manage state between SwiftUI views by using `@ StateObject` and `@ ObservedObject`. This guide breaks down the essential steps for sharing a single `viewModel` across multiple views in a `TabView`.
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Managing State Between Views in SwiftUI

In SwiftUI, it’s common to have multiple views that need to share data or manage state between them. In this post, we will explore how to properly initialize a View by observing an @ StateObject from other Views. This can become particularly useful when working with complex user interfaces, such as when using a TabView to switch between different functionalities in your application.

The Problem: Sharing a ViewModel Across Multiple Views

Let’s consider an example. Imagine you have two views within a TabView in your SwiftUI app: one for adding new employees (AddEmployeeView) and another for displaying a list of all employees (AllEmployeesView). You have a ViewModel (EmployeeViewModel) that holds the employee data, and you want to access this same viewModel instance in both views.

If you try to initialize AllEmployeesView directly within your TabView, you encounter an error stating, "Missing argument for parameter 'viewModel' in call." This indicates that SwiftUI expects a viewModel parameter to be passed into AllEmployeesView, but since it's missing, it throws an error.

The Solution: Single Source of Truth

To solve this issue and ensure that both views can access the same instance of the viewModel, you should define your viewModel in the main view (in this case, ContentView) and then pass it to the child views as needed. Here's a step-by-step guide on how to do this:

Step 1: Declare viewModel in ContentView

First, create a @ StateObject for your viewModel in ContentView. This makes ContentView the single source of truth for your state:

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Step 2: Modify Child Views to Accept the ViewModel

Adjust both AddEmployeeView and AllEmployeesView to accept the viewModel as a parameter. Here's how to do it:

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

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

Conclusion: Keeping Everything in Sync

By following the steps above, all three views (ContentView, AddEmployeeView, and AllEmployeesView) now refer to the same instance of EmployeeViewModel. This ensures that any updates made in one view are reflected in the others seamlessly. Now, your TabView functions correctly without any errors and maintains synchronized state across views.

Using this approach not only resolves the sharing issue but also promotes better state management in your SwiftUI applications. Happy coding!