OnNotFirstTime.swift

private struct OnFirstAppear: ViewModifier {
    let perform: () -> Void
    let `else`: () -> Void

    @State private var firstTime = true

    func body(content: Content) -> some View {
        content.onAppear {
            if firstTime {
                firstTime = false
                perform()
            } else {
                `else`()
            }
        }
    }
}

private struct OnNotFirstAppear: ViewModifier {
    let perform: () -> Void

    @State private var firstTime = true

    func body(content: Content) -> some View {
        content.onAppear {
            if firstTime {
                firstTime = false
            } else {
                perform()
            }
        }
    }
}

extension View {
    func onFirstAppear(perform: @escaping () -> Void, else: @escaping () -> Void = { }) -> some View {
        modifier(OnFirstAppear(perform: perform, else: `else`))
    }

    func onNotFirstAppear(perform: @escaping () -> Void) -> some View {
        modifier(OnNotFirstAppear(perform: perform))
    }
}