SwiftUI Frame Reader

FrameReader.swift

import SwiftUI

extension View {
    func frameReader(frame: Binding<CGRect>) -> some View {
        modifier(FrameReaderModifier(frame: frame))
    }
}

struct FrameReaderModifier: ViewModifier {
    @Binding var frame: CGRect
    
    func body(content: Content) -> some View {
        content
            .background {
                GeometryReader { geometry in
                    Color.clear
                        .preference(key: FramePreferenceKey.self,
                                    value: geometry.frame(in: .local))
                }
                .onPreferenceChange(FramePreferenceKey.self) { newValue in
                    guard frame != newValue else { return }
                    frame = newValue
                }
            }
    }
}

struct FramePreferenceKey: PreferenceKey {
    static var defaultValue: CGRect = .zero
    
    static func reduce(value: inout CGRect, nextValue: () -> CGRect) {
        value = nextValue()
    }
}

Usage.swift

import SwiftUI

struct ContentView: View {
    @State private var frame: CGRect = .zero
    
    var body: some View {
        VStack {
            Text("Hello, world!")
        }
        .frameReader(frame: $frame)
    }
}