SwiftUIListMacOS.swift

import SwiftUI

@main
struct SwiftUIListVSLazyVStackApp: App {
    
    let numbers = (0...100).map { $0 }
    
    var body: some Scene {
        WindowGroup {
            /*
             List calls the init & the body of *every* element on the list, even if it's not being displayed making it extremely slow.
             */
            List(numbers) { number in
                RowView(for: number, example: "list")
            }
            
            /*
             A combination of ScrollView + LazyVStack achieves what's expected from the list. Only calls the init & body of
             the element that's going to be displayed.
             */
//            ScrollView {
//                LazyVStack(alignment: .leading, spacing: 8) {
//                    ForEach(numbers) { number in
//                        RowView(for: number, example: "stack")
//                    }
//                }
//            }
        }
    }
}

struct RowView: View {
    
    private let number: Int
    private let example: String
    
    init(for number: Int, example: String) {
        print("Init \(example): \(number)")
        self.number = number
        self.example = example
    }
    
    var body: some View {
        let _ = print("Body \(example): \(number)")
        Text("\(number)")
            .onAppear{ print("Appear \(example): \(number)") }
    }
}

extension Int: Identifiable {
    public var id: Int { self }
}

I realized about this due to performance issues. Look how different the behavior is when the list has 100_000 rows.

1. List took ~12 seconds to render
2. ScrollView + LazyVStack rendered instantly

Example.100K.mov