In SwiftUI, where are the control events, i.e. scrollViewDidScroll to detect the bottom of list data

Question

In SwiftUI, does anyone know where are the control events such as scrollViewDidScroll to detect when a user reaches the bottom of a list causing an event to retrieve additional chunks of data? Or is there a new way to do this?

Seems like UIRefreshControl() is not there either...

Answer 1

Plenty of features are missing from SwiftUI - it doesn't seem to be possible at the moment.

But here's a workaround.

TL;DR skip directly at the bottom of the answer

An interesting finding whilst doing some comparisons between ScrollView and List:

struct ContentView: View {

    var body: some View {

        ScrollView {
            ForEach(1...100) { item in
                Text("\(item)")
            }
            Rectangle()
                .onAppear { print("Reached end of scroll view")  }
        }
    }

}

I appended a Rectangle at the end of 100 Text items inside a ScrollView, with a print in onDidAppear.

It fired when the ScrollView appeared, even if it showed the first 20 items.

All views inside a Scrollview are rendered immediately, even if they are offscreen.

I tried the same with List, and the behaviour is different.

struct ContentView: View {

    var body: some View {

        List {
            ForEach(1...100) { item in
                Text("\(item)")
            }
            Rectangle()
                .onAppear { print("Reached end of scroll view")  }
        }
    }

}

The print gets executed only when the bottom of the List is reached!

So this is a temporary solution, until SwiftUI API gets better.

Use a List and place a "fake" view at the end of it, and put fetching logic inside onAppear { }

Answer 2

You can to check that the latest element is appeared inside onAppear.

struct ContentView: View {
    @State var items = Array(1...30)

    var body: some View {
        List {
            ForEach(items, id: \.self) { item in
                Text("\(item)")
                .onAppear {
                    if let last == self.items.last {
                        print("last item")
                        self.items += last+1...last+30
                    }
                }
            }
        }
    }
}