reader_of_prefs.swift

struct KeyboardAvoiderPreferenceReader: ViewModifier {
    
    let tag: Int
    
    func body(content: Content) -> some View {
        
        content
            .background(
                GeometryReader { geometry in
                    Rectangle()
                        .fill(Color.clear)
                        .preference(
                            key: KeyboardAvoiderPreferenceKey.self,
                            value: [
                                KeyboardAvoiderPreference(tag: self.tag, rect: geometry.frame(in: .global))
                        ])
                }
            )
    }
}