如何存储符合 ListStyle 协议的属性

Question

目前我正在使用.listStyle(InsetGroupedListStyle()) 修饰符设置listStyle。

struct ContentView: View {
    var body: some View {
        ListView()
    }
}

struct ListView: View {
    let data = ["One", "Two", "Three", "Four", "Five", "Six"]
    var body: some View {
        List {
            ForEach(data, id: \.self) { word in
                Text(word)
            }
        }
        .listStyle(InsetGroupedListStyle())
    }
}

我想在ListView 中创建一个属性来存储ListStyle。问题是ListStyle 是一个协议，我得到：

Protocol 'ListStyle' 只能用作通用约束，因为 它有 Self 或关联的类型要求

struct ContentView: View {
    var body: some View {
        ListView(listStyle: InsetGroupedListStyle())
    }
}

struct ListView: View {
    var listStyle: ListStyle /// this does not work
    let data = ["One", "Two", "Three", "Four", "Five", "Six"]
    var body: some View {
        List {
            ForEach(data, id: \.self) { word in
                Text(word)
            }
        }
        .listStyle(listStyle)
    }
}

我看了这个question，但我不知道ListStyle的associatedtype是什么。

Answer 1

您可以使用泛型使您的listStyle 成为一些 ListStyle 类型：

struct ListView<S>: View where S: ListStyle {
    var listStyle: S
    let data = ["One", "Two", "Three", "Four", "Five", "Six"]
    var body: some View {
        List {
            ForEach(data, id: \.self) { word in
                Text(word)
            }
        }
        .listStyle(listStyle)
    }
}