WidthPreference

@available(iOS 13.0, macOS 10.15, tvOS 13.0, watchOS 6.0, *)
struct WidthPreference : PreferenceKey

Collects width of all the cells, with reduce takes the maximum value for the given key


                    
                    
                    reduce(value:nextValue:)

Swift

static func reduce(value: inout Value, nextValue: () -> Value)