swift - 如何在 SwiftUI 列表中获取行索引？

Question

我想要一个编号列表，其中每一行都有一个数字。

像这样

但我在 List 初始化器中没有看到正确的 API

此刻我看到了这个解决方法

var persons = ["Boris", "Anna", "Tom"]

// MARK: - Body
func body(props: Props) -> some View {
    List(persons.indices, id: \.self) { index in
        Text("\(index) \(self.persons[index])")
    }
}

Answer 1

使用 .indices() 不是解决方法，而是一种正确的方法。

或者，您也可以使用发行说明中的​​代码来创建 indexed() 数组:

struct ContentView: View {
    var persons = ["Boris", "Anna", "Tom"]

    var body: some View {
        VStack {
            List(persons.indexed(), id: \.1.self) { idx, person in
                Text("\(idx) - \(person)")
            }
        }
    }
}


// This is taken from the Release Notes, with a typo correction, marked below
struct IndexedCollection<Base: RandomAccessCollection>: RandomAccessCollection {
    typealias Index = Base.Index
    typealias Element = (index: Index, element: Base.Element)

    let base: Base

    var startIndex: Index { base.startIndex }

   // corrected typo: base.endIndex, instead of base.startIndex
    var endIndex: Index { base.endIndex }

    func index(after i: Index) -> Index {
        base.index(after: i)
    }

    func index(before i: Index) -> Index {
        base.index(before: i)
    }

    func index(_ i: Index, offsetBy distance: Int) -> Index {
        base.index(i, offsetBy: distance)
    }

    subscript(position: Index) -> Element {
        (index: position, element: base[position])
    }
}

extension RandomAccessCollection {
    func indexed() -> IndexedCollection<Self> {
        IndexedCollection(base: self)
    }
}