基于GeometryReader结果运行条件代码的视图扩展

import SwiftUI

struct ContentView: View {
    var body: some View {
        VStack {
            Text("Hello, World!")
                .foregroundColor(.white)
                .padding()
                .background(Color.blue)
                .cornerRadius(10)
                .runCodeOnSizeChange { size in
                    if size.width > 200 {
                        print("View width is greater than 200")
                    } else {
                        print("View width is less than or equal to 200")
                    }
                }
        }
    }
}

extension View {
    func runCodeOnSizeChange(code: @escaping (CGSize) -> Void) -> some View {
        self.background(
            GeometryReader { geometry in
                Color.clear
                    .preference(key: SizePreferenceKey.self, value: geometry.size)
            }
        )
        .onPreferenceChange(SizePreferenceKey.self, perform: code)
    }
}

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