Swift UI vie modifier for retrieving the view size

SwiftUI_SizeChangeModifier.swift

import SwiftUI

public extension View {
  func onSizeChange(
    ignoreSafeArea: Bool = false,
    round: Bool = false,
    perform action: @escaping (CGSize) -> Void
  ) -> some View {
    modifier(SizeChangeModifier(
      ignoreSafeArea: ignoreSafeArea,
      round: round,
      onSizeChange: action
    ))
  }
}

private struct SizeChangeModifier: ViewModifier {
  var ignoreSafeArea: Bool
  var round: Bool
  var onSizeChange: (CGSize) -> Void

  func body(content: Content) -> some View {
    content
      .background(
        GeometryReader { geometry in
          Color.clear.preference(key: SizePreferenceKey.self, value: size(from: geometry))
            .onPreferenceChange(SizePreferenceKey.self, perform: onSizeChange)
        }
      )
  }

  func size(from proxy: GeometryProxy) -> CGSize {
    var size = proxy.size
    if ignoreSafeArea {
      size.width += proxy.safeAreaInsets.leading + proxy.safeAreaInsets.trailing
      size.height += proxy.safeAreaInsets.top + proxy.safeAreaInsets.bottom
    }
    if round {
      size.width = size.width.rounded()
      size.height = size.height.rounded()
    }
    return size
  }

  struct SizePreferenceKey: PreferenceKey {
    static var defaultValue: CGSize = .zero

    static func reduce(value: inout CGSize, nextValue: () -> CGSize) {
      value = nextValue()
    }
  }
}

// MARK: - Example

struct ExampleView: View {
  var body: some View {
    Text("Hello, World")
      .onSizeChange { size in
        print("size of the view = \(size)")
      }
  }
}