SwiftUI 更改 macOS 的文本大小

Question

Using SwiftUI for a small all and I noticed that the font size is very small on macOS

var body: some View {
        VStack {
            NavigationView {
                List(fetch.Novitadss) { Novitads in
                    VStack(alignment: .leading) {
                        // 3.
                        Text(Novitads.title)
                            .font(.headline)
                            .fontWeight(.regular)
                            .onTapGesture {
                                UIApplication.shared.open(URL(string: Novitads.link)!)
                            }
                    }
                }

I would like to add a condition to change the.font(.headline) if os is macOS so I tried

                         #if os(iOS)
                            .font(.headline)
                        #elseif os(macOS)
                               .font(.title)
                        #endif

but I get "Unexpected platform condition (expected 'os', 'arch', or 'swift')"

Answer 1

From your comment , you asked why your code did not work, which I will explain in my answer.

According to the documentation , a conditional compilation block has the following syntax:

Notice that it says "statements" inside the block. .font(.headline) is not a statement, so it is illegal to put that there. This is also evident in the formal grammar notation further down the page:

In addition, in the "Note" block just above the formal grammar:

Each statement in the body of a conditional compilation block is parsed even if it's not compiled. However, there is an exception if the compilation condition includes a swift() platform condition.

This explains why your #elseif block has the error as well.

In other words, #if statements are not your C++ preprocessor directives:)

Therefore, to fix the problem, you must put a whole statement in those blocks. One (dumb) way to fix this would be:

 #if os(iOS)
Text(Novitads.title)
    .font(.headline)
    .fontWeight(.regular)
    .onTapGesture {
        UIApplication.shared.open(URL(string: Novitads.link)!)
    }
#elseif os(macOS)
Text(Novitads.title)
    .font(.title)
    .fontWeight(.regular)
    .onTapGesture {
        // UIApplication.shared.open(URL(string: Novitads.link)!)
        // you would use this on macOS to open URLs, right?
        NSWorkspace.shared.open(URL(string: Novitads.link)!)
    }
#endif

Of course, Asperi's solution of extracting a platformFont method is a lot better.

Answer 2

You can use the following helper extension

extension Text {
    func platformFont() -> Text {
#if canImport(AppKit) || targetEnvironment(macCatalyst)
        return self.font(.title)
#elseif canImport(UIKit)
         return self.font(.headline)
#else
        return self
#endif
    }
}

and usage

Text(Novitads.title)
   .platformFont()

Update: Added demo. Tested with Xcode 11.4 / macOS 10.15.4

struct ContentView: View {
    var body: some View {
        VStack {
            Text("Hello World!")
            Text("Hello World!").platformFont()
        }
    }
}

Answer 3

Please check this article It should be like this:

#if targetEnvironment(macCatalyst)
return self.font(.largeTitle)
#elseif os(iOS)
return self.font(.system(size: 10))
#else
return self
#endif