Compiler directives in SwiftUI for platform-specific attributes

Question

Created Jul ’20

Replies 4

Boosts 0

Views 6.6k

Participants 4

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

Answered by OOPer in 619668022

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
		}

Boost

Answer 1

OOPer OP

Jul ’20

Accepted Answer

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
		}

5

Answer 2

corybohon OP

Jul ’20

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!

0

Answer 3

sindresorhus OP

Jul ’20

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

0

Answer 4

DandyLyons OP

Jul ’21

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

0