iOS 15 only view modifier causes crash on iOS 14 even with if #available(iOS 15.0, *)

Question

I'm using SwiftUI's drag & drop modifiers. Since, iOS 15 gives an option to customise the onDrag modifier with a preview I'm using it as shown below.

Issue: I've a if #available(iOS 15.0, *) guard to choose the view for different iOS versions. But, somehow my app on iOS 14.x crashes due to an EXC_BAD_ACCESS (code=1, address=0x0) error since it tries to find the new API but it is not present in iOS 14.

@ViewBuilder
private func getRoutineCard(routine: RoutineInfo) -> some View {
    if #available(iOS 15.0, *) {
        newRoutineCard(routine: routine)
    } else {
        oldRoutineCard(routine: routine)
    }
}

@available(iOS 15.0, *)
@ViewBuilder
private func newRoutineCard(routine: RoutineInfo) -> some View {
    RoutineCard(routine: routine)
    // This modifier is what crashes the app on iOS 14.x
    // onDrag with a drag preview view not available in iOS 14.x
        .onDrag({
            dragReorder(draggedRoutine: routine)
        }, preview: {
            RoutineCardDragPreview(routine: routine)
        })
        .onDrop(of: [.text], delegate: ReorderDropDelegate(isDragging: $isDragging, draggedItem: $draggedItem, item: routine, haptics: haptics, onMove: updateOrder(routine:order:)))
}

@ViewBuilder
private func oldRoutineCard(routine: RoutineInfo) -> some View {
    RoutineCard(routine: routine)
        .onDrag { dragReorder(draggedRoutine: routine) }
        .onDrop(of: [.text], delegate: ReorderDropDelegate(isDragging: $isDragging, draggedItem: $draggedItem, item: routine, haptics: haptics, onMove: updateOrder(routine:order:)))
}

What I'm looking for: A workaround to choose between the two views based on the iOS version without causing a crash.

The solution might be to make your own ViewModifiers, this seems to be a known issue https://developer.apple.com/forums/thread/688678 here is a workaround that the pointfree guys did https://github.com/pointfreeco/swift-composable-architecture/pull/931/files — Andrew, Dec 27 '21 at 21:04
@Andrew Thank you for that github link. I did end up creating a view modifier and it works as expected. — Siddharth Kamaria, Dec 28 '21 at 10:31
That’s great that you got it working. Why don’t you write up your solution so that it can benefit the community? — Andrew, Dec 28 '21 at 13:47

score 6 · Answer 1 · answered Jan 06 '22 at 07:21

6

To anyone stumbling upon this:

When using if #available(iOS 14.0, OSX 11.0, *) inside a ViewBuilder, the application crashes when running on the fallback side.

This happens with Xcode versions 13.1 and above. (Currently Xcode 13.2.1) Tested out with Xcode 13.0 build and crash is gone. We think this is because of compiler optimisation bug in Xcode. For development builds we do not have these crashes.

More here: https://swiftui-lab.com/bug-os-check/ and same answer: Swiftui app crashes with different SearchBar (ViewModifier) on iOS 14 / 15

answered Jan 06 '22 at 07:21

Lukas

2,515
4
28
37

"For development builds we do not have these crashes" - I can attest to that. It was working fine locally in Debug mode. – Siddharth Kamaria Jan 06 '22 at 08:16
The crash happens because Xcode 13.1+ Swift compiler code optimizer does some black magic which is darker than it should've been. Setting Swift Compiler Optimization Level parameter to "None" solves the issue... – Serzhas Jan 25 '22 at 09:16

score 0 · Answer 2 · answered Apr 18 '22 at 06:50

0

It's due to the code which is written in ViewBuilder. That needs to be transferred to View Modifier

Got solution https://stackoverflow.com/a/71908419/9970928

answered Apr 18 '22 at 06:50

Manish

608
1
11
23

iOS 15 only view modifier causes crash on iOS 14 even with if #available(iOS 15.0, *)

2 Answers2