在 swiftUI 中是否可以使用按钮在屏幕上添加新视图？

Question

每次点击按钮时，我都希望出现一个新的 cardView。我想知道这在 swiftUI 中是否可行，如果可以，我需要采取什么行动。如果我能够将一些参数传递给 cardView 结构会更好，但任何帮助都会很棒！

struct ContentView: View {
    var body: some View {
        ZStack {
            VStack {
                TextButton(action: {print("Button tapped")}, text: "new card")
                CardView()
            }
        }
    }
}

struct CardView: View {
    var body: some View {
        ZStack {
            Rectangle()
                .fill(Color(#colorLiteral(red: 0.7450980544, green: 0.1568627506, blue: 0.07450980693, alpha: 1)))
                .frame(width: 100, height: 100 * 1.618)
                .cornerRadius(16)
                .shadow(color: Color(#colorLiteral(red: 0, green: 0, blue: 0, alpha: 1)).opacity(0.1), radius: 1, x: 0, y: 1)
                .shadow(color: Color(#colorLiteral(red: 0, green: 0, blue: 0, alpha: 1)).opacity(0.2), radius: 10, x: 0, y: 10)

            VStack {
                Text("Card")
                    .font(.system(size: 10) )
                    .foregroundColor(.white)
                    .bold()
            }
        }
    }
}


struct TextButton: View {
    let action: () -> Void
    let text: String

    var body: some View {
        Button(action: action, label: {
            Text(text)
                .padding(.horizontal, 16)
                .padding(.vertical, 16)
                .foregroundColor(.white)
                .background(Color.blue)
                .cornerRadius(.infinity)
                .shadow(color: Color(#colorLiteral(red: 0, green: 0, blue: 0, alpha: 1)).opacity(0.1), radius: 1, x: 0, y: 1)
                .shadow(color: Color(#colorLiteral(red: 0, green: 0, blue: 0, alpha: 1)).opacity(0.2), radius: 10, x: 0, y: 10)
        })
    }
}
struct ContentView_Previews: PreviewProvider {
    static var previews: some View {
        ContentView()
    }
} ```

Answer 1

在 SwiftUI 中，View 反映的是 State 数据，所以你不直接修改 View，而是修改 State 数据，基于 State 构建 View。这是 SwiftUI 背后的核心原则，它允许您将 View 关注点与驱动它的数据（在某些术语中为 ViewModel）分开。

所以，假设我们有一个Card 的数据模型（使其符合Identifiable - 这将在以后需要）：

struct Card: Identifiable {
  let id = UUID()
  let name: String
}

让我们在你的视图中定义一个卡片数组作为状态变量：

@State private var cards: [Card] = [Card(name: "foo")]

然后主体可以使用ForEach 或List 视图显示这些卡片：

var body = some View {
  VStack() {
    Button("Add Card") {
       self.cards.append(Card(name: "I'm an added card"))
    }
    ForEach(cards) { card in
       CardView(for: card) // if your CardView had parameters
    }
  }
}

发生的情况是按钮的闭包向cards 状态变量添加了一个新的Card 实例。就是这样。它不会直接更改视图中的任何内容。 View 看到变化（这就是 SwiftUI 在幕后所做的）并重新渲染自己。

您需要Card 以符合Identifiable 的原因是让ForEach 知道如何唯一标识每张卡。在不符合可识别的情况下，您可以使用这样的关键路径：

ForEach(cards, id: \.self) { card in
  // ...
}

Answer 2

看看这个：

import SwiftUI

struct ContentView: View {

    @State var cards: [CardView] = [CardView()]



    var body: some View {
        VStack {
            TextButton(action: {
                print("Button tapped")
                self.cards.append(CardView())

            }, text: "new card")
            ZStack {
                ForEach(cards, id: \.self) { card in
                    card
                        .rotationEffect(card.angle)

                }

            }
        }
    }
}

struct CardView: View, Hashable, Identifiable {

    var id = UUID()

    var angle : Angle {
        let angle = Angle(degrees: Double.random(in: 0...30))
        print(angle.degrees)
        return angle
    }
    var body: some View {
        ZStack {
            Rectangle()
                .fill(Color(#colorLiteral(red: 0.7450980544, green: 0.1568627506, blue: 0.07450980693, alpha: 1)))
                .frame(width: 100, height: 100 * 1.618)
                .cornerRadius(16)
                .shadow(color: Color(#colorLiteral(red: 0, green: 0, blue: 0, alpha: 1)).opacity(0.1), radius: 1, x: 0, y: 1)
                .shadow(color: Color(#colorLiteral(red: 0, green: 0, blue: 0, alpha: 1)).opacity(0.2), radius: 10, x: 0, y: 10)

            VStack {
                Text("Card \(angle.degrees)")
                    .font(.system(size: 10) )
                    .foregroundColor(.white)
                    .bold()
            }
        }
    }
}


struct TextButton: View {
    let action: () -> Void
    let text: String

    var body: some View {
        Button(action: action, label: {
            Text(text)
                .padding(.horizontal, 16)
                .padding(.vertical, 16)
                .foregroundColor(.white)
                .background(Color.blue)
                .cornerRadius(.infinity)
                .shadow(color: Color(#colorLiteral(red: 0, green: 0, blue: 0, alpha: 1)).opacity(0.1), radius: 1, x: 0, y: 1)
                .shadow(color: Color(#colorLiteral(red: 0, green: 0, blue: 0, alpha: 1)).opacity(0.2), radius: 10, x: 0, y: 10)
        })
    }
}
struct ContentView_Previews: PreviewProvider {
    static var previews: some View {
        ContentView()
    }
}