Can someone explain how exactly does the "LoadThenNavigate" case study work?

[phi161]

I am studying the LoadThenNavigate example and even if I can follow what happens after LoadThenNavigateAction.setNavigation(isActive: true) is sent, I can't understand who sends this action.

Does tapping on the row cause the isActive binding to send the LoadThenNavigateAction.setNavigation action? And if yes, why is its isActive associated value set to true? I would expect it to be false, because isNavigationActive is also false.

[mbrandonw]

That case study demonstrates how to execute some logic before causing a drill-down navigation. Like if you wanted to perform an API request and then with the result of that request decide whether you do the drill-down or show an error message.

So when you tap the nav link, a setNavigation(true) action is sent, but we don't actually update state to have isNavigationActive=true. Instead, we fire off an effect, and when the effect finishes we then set isNavigationActive=true which then causes the drill-down to happen.

Does that help?

[phi161]

So when you tap the nav link, a setNavigation(true) action is sent

This is the part I don't understand - the isActive binding looks like this:

viewStore.binding(
            get: \.isNavigationActive,
            send: LoadThenNavigateAction.setNavigation(isActive:)
          )

How come and tapping on the link sends setNavigation(true)?

[mbrandonw]

That is just how SwiftUI works. The boolean binding you hand to NavigationLink.init(isActive) gets true written to it when it is tapped. We then intercept that true and send an action to the view instead of writing state directly, which gives us the opportunity to layer on logic before actually performing the navigation.

[phi161]

Perfect, I get it now - thanks a lot for the quick replies!