SwiftUI中Toggle需点击两次才生效问题排查求助

我在SwiftUI中实现了一个展示书籍的List，每本Book模型包含isFinished属性。用户点击书籍可进入详情页，在详情页通过Toggle切换书籍的isFinished状态。目前遇到的问题是：首次点击Toggle无法改变状态，需点击两次才能完成状态切换。

原始完整代码 #

struct Book: Hashable, Identifiable {
    let id = UUID()
    let name: String
    var isFinished: Bool = true
}

struct BookCellView: View {
    
    let book: Book
    
    var body: some View {
        HStack {
            Text(book.name)
            Text(book.isFinished ? "Finished": "Not finished")
        }
    }
}

struct BookDetailView: View {
    
    @Binding var book: Book
    @State private var isOn: Bool = false
    
    var body: some View {
        VStack {
            Text(book.name)
            Toggle(isOn: $book.isFinished) {
                Text("Finished")
            }.fixedSize()
        }
    }
}

struct ContentView: View {
    
    @State private var books = [Book(name: "Harry Potter"), Book(name: "Peek Performance"), Book(name: "Ready Player One")]
    
    func bookBinding(id: UUID) -> Binding<Book> {
        
        let index = books.firstIndex(where: { $0.id == id })!
        
        return Binding {
            return books[index]
        } set: {
            books[index] = $0
        }

    }
    
    var body: some View {
        NavigationStack {
            List(books) { book in
                
                NavigationLink(value: book) {
                    BookCellView(book: book)
                }
            }.navigationDestination(for: Book.self) { book in
                BookDetailView(book: bookBinding(id: book.id))
            }
        }
    }
}

更新后的代码 #

struct ContentView: View {
    
    @State private var books = [Book(name: "Harry Potter"), Book(name: "Peek Performance"), Book(name: "Ready Player One")]
    
    /*
    func bookBinding(id: UUID) -> Binding<Book> {
        
        let index = books.firstIndex(where: { $0.id == id })!
        
        return Binding {
            return books[index]
        } set: {
            books[index] = $0
        }

    } */
    
    var body: some View {
        NavigationStack {
            List(books) { book in
                
                NavigationLink(value: book.id) {
                    BookCellView(book: book)
                }
            }.navigationDestination(for: UUID.self) { id in
                let index = books.firstIndex(where: { $0.id == id })!
                BookDetailView(book: $books[index])
            }
        }
    }
}

问题原因与修复说明 #

问题根源 #

原始代码的核心问题在于值类型的传递方式：

• Book是struct值类型，NavigationLink(value: book)传递的是当前book的副本，而非对原数组元素的引用。
• 虽然通过bookBinding方法基于原数组索引创建了Binding，但详情页视图初始化时依赖的是传递过来的book副本，导致SwiftUI的状态追踪出现延迟：第一次点击Toggle修改状态后，原数组元素已更新，但详情页视图未及时感知，需要第二次点击才能触发视图刷新完成同步。

修复逻辑 #

更新后的代码通过两个关键调整解决了问题：

1. 传递book.id而非book本身，彻底避免值类型副本传递带来的视图同步问题。
2. 在navigationDestination中直接通过ID定位原数组索引，使用$books[index]创建直接绑定到原@State数组元素的Binding，确保状态修改能立即同步并触发视图更新。

另外，BookDetailView中声明的@State private var isOn: Bool = false是未使用的冗余代码，可安全删除。

内容的提问来源于stack exchange，提问作者user19037628