为什么在将照片从照片拾取器添加到SwiftUI中的模型时保持视图更新？

import SwiftUI

struct ContentView: View {
    @State private var photos: [UIImage] = []

    var body: some View {
        VStack {
            ForEach(photos, id: \.self) { photo in
                Image(uiImage: photo)
                    .resizable()
                    .scaledToFit()
            }
            
            Button("Add Photo") {
                // 假设pickPhoto()是一个获取照片的方法
                if let newPhoto = pickPhoto() {
                    photos.append(newPhoto)
                }
            }
        }
    }

    func pickPhoto() -> UIImage? {
        // 实现照片拾取逻辑
        return UIImage(named: "example")
    }
}

struct ContentView_Previews: PreviewProvider {
    static var previews: some View {
        ContentView()
    }
}