Differences between SwiftUI in Monterey and Sequoia

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Created 12h

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Having written a SwiftUI based app on macOS 15.2 with Xcode 16.2 I built a version for Monterey (which required backing off some modern uses, like #Preview and others). But the SwiftUI layout, positioning and dimensions, didn't use anything new so,

I was surprised that the app did not look exactly the same on Monterey. It was not wildly different, but enough that I had to modify several to frame, padding and font parameters in order to restore my desired appearance.

I'm assuming that over the course of generations of SwiftUI, things change -- that's life, but this was a frustrating process for at least two reasons:

view modifiers can't be conditionally compiled so something like this, for example, isn't possible

    RoundedRectangle(cornerRadius: 1)
<if Monterey>
        .padding(.horizontal, -2.0)
<else>      
        .padding(.horizontal, -4.0)
<endif>
        .frame(height: 4.0)

previewing views is a challenge. Previewing on Sequoia doesn't show what the views will look like on Monterey. I can build the app on Monterey and use the non-macro #preview mechanism, but in order to do that, and the above, I'm pushed to maintain two versions of my app because the following doesn't compile:
```
#if swift(>=5.9)
#Preview("Monitor") { MonitorView() }
#else
struct MonitorView_Previews: PreviewProvider {
    static var previews: some View { 
        MonitorView() 
    }
}
#endif
```

These are not show-stoppers but I do wonder if I'm missing some mechanism(s) to ease the pain, or if SwiftUI functional changes are documented.

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Answer 1

Claude31 OP

9h

Yes, the syntax you are looking for would be convenient…

But you can do it a bit differently.

Like this

    func conditionalRect() -> some View {
        if #available(macOS 16.0, *) {
            return RoundedRectangle(cornerRadius: 1)
                .padding(.horizontal, -2.0)
                .frame(height: 4.0)
        } else {
            return RoundedRectangle(cornerRadius: 1)
                .padding(.horizontal, -4.0)
                .frame(height: 4.0)  
         }
    }

Or more simply, create a computed var

var horizPadding : CGFloat {
        if #available(macOS 16.0, *) {
            return -2.0
        } else {
            return -4.0  
        }
}

Then call

    RoundedRectangle(cornerRadius: 1)
        .padding(.horizontal, horizPadding)
        .frame(height: 4.0)

1