Compiler directives in SwiftUI for platform-specific attributes

Question

I'm building a universal application with SwiftUI that has an iOS app and Share Extension as well as a macOS app and Share Extension.

There's a few places where I'm using SwiftUI attributes that are iOS-specific (example a NavigationView that has a StackNavigationViewStyle attribute) and need to provide an alternative when running on macOS.

My question is: How do I ensure that these attributes that are only available for one platform don't cause build issues for the other platform? I've tried using the #if os(iOS) compiler directive, but then I get a build error saying "Unexpected platform condition (expected 'os' 'arch' or 'swift')" when doing something like this:

Code Block swift				NavigationView {
						...
				}
        #if os(iOS)			
				.navigationViewStyle(StackNavigationViewStyle())
        #endif

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Posted by

corybohon

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I believe this feature was added in Swift 5.4 Swift by sundell has an article about it.

—
DandyLyons

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Answer 1

In #if compiler directive in Swift, you need to enclosed valid statements.

As you can see, .navigationViewStyle(StackNavigationViewStyle()) is not a valid statement.

You may need to write something like this:

Code Block 		#if os(iOS)
		var body: some View {
				NavigationView{
						...
				}
				.navigationViewStyle(StackNavigationViewStyle())
		}
		#else
		var body: some View {
				NavigationView{
						...
				}
				.navigationViewStyle(DoubleColumnNavigationViewStyle())
		}
		#endif

Or this:

Code Block 		var body: some View {
				let navView = NavigationView{
						...
				}
				#if os(iOS)
				return navView
						.navigationViewStyle(StackNavigationViewStyle())
				#else
				return navView
						.navigationViewStyle(DoubleColumnNavigationViewStyle())
				#endif
		}

Posted by

OOPer

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Answer 2

In #if compiler directive in Swift, you need to enclosed valid statements.

As you can see, .navigationViewStyle(StackNavigationViewStyle()) is not a valid statement.

You may need to write something like this:

Code Block 		#if os(iOS)
		var body: some View {
				NavigationView{
						...
				}
				.navigationViewStyle(StackNavigationViewStyle())
		}
		#else
		var body: some View {
				NavigationView{
						...
				}
				.navigationViewStyle(DoubleColumnNavigationViewStyle())
		}
		#endif

Or this:

Code Block 		var body: some View {
				let navView = NavigationView{
						...
				}
				#if os(iOS)
				return navView
						.navigationViewStyle(StackNavigationViewStyle())
				#else
				return navView
						.navigationViewStyle(DoubleColumnNavigationViewStyle())
				#endif
		}

Posted by

OOPer

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Answer 3

I was hoping there would be some other way other than defining another body var. Thanks for the reply — I'll give abstracting out the views a try and then using the second example!

Posted by

corybohon

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Answer 4

If you don't want to duplicate body, you can make use of a View extension: https://stackoverflow.com/a/62099616/64949

Posted by

sindresorhus

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Compiler directives in SwiftUI for platform-specific attributes

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