Conditional modifiers: if #available iOS 14

Question

Belacqua2000 OP

Created Jul ’20

Replies 4

Boosts 0

Views 11k

Participants 4

I would love my SwiftUI views to support the new modifiers in iOS 14 (e.g. .navigationTitle), but still run on iOS 13 (e.g. using deprecated .navigationBarTitle). What is the best way to add conditional #if available code for view modifiers?

The only way I can find to do it is by extracting every subview, and putting #if available blocks around every view declaration — this seems very tedious, as I am redefining each view twice.

E.g.

Code Block Swiftstruct SettingsView: View {
    var body: some View {
        NavigationView {
            if #available(iOS 14.0, *) {
                SettingsContentView()
                    .navigationTitle("Settings")
            } else {
                SettingsContentView()
                    .navigationBarTitle("Settings")
            }
        }
    }
}

Is there a better way to just add conditional code only around the modifiers? Thanks in advance.

Boost

Answer 1

JakeShort OP

Jul ’20

You can create a custom modifier to handle this, like so:

Code Block Swift@available(iOS 14, *)
struct NavigationTitleViewModifier: ViewModifier {
	var text: String
	
	func body(content: Content) -> some View {
		content
			.navigationTitle(text)
	}
}
struct NavigationBarTitleViewModifier: ViewModifier {
	var text: String
	
	func body(content: Content) -> some View {
		content
			.navigationBarTitle(text)
	}
}
extension View {
	@ViewBuilder
	func customNavigationTitle(with text: String) -> some View {
		if #available(iOS 14, *) {
			self
				.modifier(NavigationTitleViewModifier(text: text))
		}
		else {
			self.modifier(NavigationBarTitleViewModifier(text: text))
		}
	}
}

Then, instead of having to write those conditionals every time you want to add a navigation title, you can simply do:

Code Block SwiftSettingsContentView()
	.customNavigationTitle(with: "Settings")

8

Answer 2

Belacqua2000 OP

Jul ’20

Thanks JakeShort, that is helpful, and would save extracting every view and passing many bindings down the view hierarchy! I've not explored the ViewBuilder property wrapper much, but noticed it when browsing the code in the Fruta sample app.

I was hoping that Apple might add built in support for this, or a ternary operator for modifiers: e.g.

Code Block SwiftMyView()
	#available (iOS 14, *) ? .navigationTitle : .navigationBarTitle

Would the ViewBuilder method work for modifiers which are new in iOS 14 and don't have an iOS 13.0 alternative? E.g.

Code Block Swift.help("Alt Text")

Another (more drastic) option I thought of would be to have two definitions for each view, an iOS 14 and iOS 13 one.

Code Block Swift@available(iOS 14.0, *)
struct Settings: View {
    var body: some View {
        Text("Hello, World")
            .navigationTitle("Title")
    }
}
struct SettingsDeprecated: View {
    var body: some View {
        Text("Hello, World")
            .navigationBarTitle("Title")
    }
}
struct ContentView: View {
    var body: some View {
        if #available(iOS 14.0, *) {
            Settings()
        } else {
            SettingsDeprecated()
        }
    }
}

But I get an "Function declares an opaque return type" error, and would be concerned about inconsistencies in keeping them both up to date.

0

Answer 3

AgileDeveloper OP

Nov ’20

@JakeShort - this is good stuff - thank you so much, was looking for that.

0

Answer 4

nivbp OP

Nov ’23

@JakeShort thank you so much! This was exactly what I needed

0