SwiftUI中数组.append方法不生效无法添加元素，求协助解决

问题原因 #

• @State属性包装器使用场景错误：@State仅适用于SwiftUI的View结构体内部存储局部状态，你自定义的DeckSetup是非View类型的普通结构体，@State在此处不会生效，对属性的修改只会作用于当前结构体的临时副本，改动不会持久留存。
• 结构体值类型特性限制：未标记mutating的结构体方法默认无法修改自身的存储属性，即便去掉@State，现有代码也无法正常修改数组内容。

修正方案 #

方案1：作为全局状态模型使用（适用于多页面共享牌组数据） #

将DeckSetup改为遵循ObservableObject协议的类，用@Published修饰需要响应变化的属性，在View层通过@StateObject持有实例即可全局同步状态：

import Foundation
import SwiftUI

class DeckSetup: ObservableObject {
    @Published var deckOCards: [String] = ["e"]
    @Published public var yourhand: [String] = []
    @Published public var dealerHand: [String] = []
    
    func setupDeck() {
        // Club Cards
        for i in 2...10 {
            deckOCards += [String(i) + " of Clubs"]
        }
        
        deckOCards.insert("Ace of Clubs", at: 0)
        deckOCards.append( "King of Clubs")
        deckOCards.append("Queen of Clubs")
        deckOCards.append("Jack of Clubs")
        
        //Heart Cards
        for i in 2...10 {
            deckOCards.append(String(i) + " of Hearts")
        }
        
        deckOCards.append("Ace of Hearts")
        deckOCards.append("King of Hearts")
        deckOCards.append("Queen of Hearts")
        deckOCards.append("Jack of Hearts")
        
        print(deckOCards.joined())
    }
}

// View层使用示例
struct GameView: View {
    @StateObject var deck = DeckSetup()
    var body: some View {
        Button("生成牌组") {
            deck.setupDeck()
        }
    }
}

方案2：作为工具结构体使用（仅用于生成牌组不需要持久状态） #

直接去掉属性包装器，给修改属性的方法加上mutating标记即可：

struct DeckSetup {
    var deckOCards: [String] = ["e"]
    public var yourhand: [String] = []
    public var dealerHand: [String] = []
    
    mutating func setupDeck() {
        // 原有逻辑保持不变
        // Club Cards
        for i in 2...10 {
            deckOCards += [String(i) + " of Clubs"]
        }
        
        deckOCards.insert("Ace of Clubs", at: 0)
        deckOCards.append( "King of Clubs")
        deckOCards.append("Queen of Clubs")
        deckOCards.append("Jack of Clubs")
        
        //Heart Cards
        for i in 2...10 {
            deckOCards.append(String(i) + " of Hearts")
        }
        
        deckOCards.append("Ace of Hearts")
        deckOCards.append("King of Hearts")
        deckOCards.append("Queen of Hearts")
        deckOCards.append("Jack of Hearts")
        
        print(deckOCards.joined())
    }
}

内容的提问来源于stack exchange，提问作者Superbia