A wrapper collection that provides items with its index using underlying collection without allocation.
In SwiftUI, we might use these following technique for using index in ForEach
.
ForEach(Array(array.enumerated()), id: \.offset) { ... }
ForEach(zip(array.indices, array), id: \.0) { ... }
There is downside like followings:
- Creating new buffer by making new collection
enumerated
provides index from 0 so that makes wrong access on using slice.
#Preview {
VStack {
ForEach.init(IndexedCollection([1, 2, 3, 4, 5]), id: \.index, content: { e in
Text("\(e.index): \(e.value)")
})
}
}
struct IdentifiableItem: Identifiable {
let id: String
let value: UUID = .init()
}
#Preview {
VStack {
ForEach.init(IndexedCollection(["a", "b", "c", "d", "e"].map(IdentifiableItem.init(id:))), content: { e in
Text("\(e.index): \(e.value)")
})
}
}
Using Group new API in iOS18. reversing z-index in a collection of view.
public struct ReversedZIndex<Content: View>: View {
private let content: Content
public init(@ViewBuilder content: () -> Content) {
self.content = content()
}
public var body: some View {
Group(
subviewsOf: content,
transform: { collection in
let count = collection.count
ForEach(IndexedCollection(collection), id: \.id) { element in
element.value
.zIndex(Double(count - element.index))
}
}
)
}
}