High CPU usage

[Schlabbi]

When using the search bar I get a high CPU usage (100% usage consistently), even when the user has not interacted with the search bar or the app at all. I only tested this on iOS 14.2.1.

Here is an example of how the high CPU usage can be reproduced quite easily:

import SwiftUI
import SwiftlySearch

class SearchViewModel: ObservableObject {
    @Published var searchText = ""
}

struct ContentView: View {
    
    @ObservedObject var viewModel = SearchViewModel()
    
    var body: some View {
        NavigationView {
            List {
                Text("foo")
            }.navigationBarSearch($viewModel.searchText)
        }
    }
}

As soon as the .navigationBarSearch is commented out, the high CPU usage disappears.

Am I doing something wrong here or could this be a bug?

[thislooksfun]

I won't be able to test this until tomorrow, but when I do it would speed up testing if I know what device(s) you have tested this on (phone, iPad, simulator, physical, etc.).

[Schlabbi]

This was tested on an iPhone 12 and an iPhone 8 Plus, both running iOS 14.2.1.

[thislooksfun]

Physical or simulator?

[Schlabbi]

I only tested on physical devices.

[thislooksfun]

I was afraid of that. I'll look into this asap, thanks for letting me know!

[Schlabbi]

I got a workaround.

When I change the @Published in the ViewModel Class to @State there won't be a high CPU usage.

As soon as it has the @Published property wrapper the updateUIViewController function will be called constantly.

Edit: When I use @State the variable won't be updated.

[thislooksfun]

I was able to reproduce the issue, and I have an idea what's causing it. If my hunch is correct, this is a bug in SwiftUI itself, though I haven't finished my analysis yet so it could be a bug in my code. In either case, the quick fix is to not store the search text in an observable object. Having an inline @State variable works as expected.

struct ContentView: View {
    
    @State var searchText = ""
    
    var body: some View {
        NavigationView {
            List {
                Text("foo")
            }.navigationBarSearch($searchText)
        }
    }
}

[thislooksfun]

@Schlabbi, this should be fixed in v1.2.3!

[JoeLago]

Was just trying to debug this behavior in my app. It seems the view keeps being rebuilt even when text isn't changing. You can set a breakpoint in the view and it will keep getting hit with no user interaction. This doesn't happen with a regular TextField eg.

    var body: some View {
        NavigationView {
            List {
                TextField("Input", text: $viewModel.searchText)
                Text("foo")
            }//.navigationBarSearch($viewModel.searchText)
        }
    }

@State won't work in my case since the UI needs to update when a published var changes.
The issue seems to persist in 1.2.3.

[thislooksfun]

@JoeLago are you sure this persists in 1.2.3? My testing showed that the cpu dropped to 0% at idle after the change.