swiftui-inline-modifier.swift

import SwiftUI
import PlaygroundSupport

/// `InlineModifier` helps you apply a view modifier in a inline block.

public struct InlineModifier<R: View>: ViewModifier {
    
    private let block: (Content) -> R
    
    public init(@ViewBuilder _ block: @escaping (Content) -> R) {
        self.block = block
    }
    
    public func body(content: Content) -> some View {
        block(content)
    }
    
}

extension View {
    
    public func modifier<T: View>(@ViewBuilder _ block: @escaping (AnyView) -> T) -> some View {
        self.modifier(InlineModifier<T>({ (content: InlineModifier<T>.Content) in
            block(AnyView(content))
        }))
    }
    
}

/// # Demo

struct ContentView: View {
    
    var body: some View {
        NavigationView {
            List {
                Text("Hello")
            }
            .modifier {
                // inline availability check for modifiers ✌️
                if #available(iOS 14.0, *) {
                    $0.listStyle(InsetGroupedListStyle())
                } else {
                    $0.listStyle(GroupedListStyle())
                      .environment(\.horizontalSizeClass, .regular)
                }
            }
            .navigationTitle("Demo")
        }
    }
    
}

PlaygroundPage.current.liveView = UIHostingController(rootView: ContentView())