How to remove duplicate set elements in SwiftUI - ios

Question

I have an entity of places called Place which has a relationship (Set<Activity>) and I am passing the places (fetch request) to the PlacesView and each place has a list of Activities. What I try to accomplish is, that instead of showing all activities related to a place directly, I want to pre-group them in date elements in a ActivityDatesView. Now I want to select the date and see all activities related to that place and date. Date is an attribute of the Activity entity.
How can I modify my code, to not display activities, that have the same activity.date (without time), where activity.date is Date() value coming from a CoreData entity and Activity is a NSManagedObject Subclass.
List(Array(place.activities as Set), id: \.self) { activity in
Text(dateFormatter.string(from: activity.date))
}
For Views, I had:
struct PlacesView {
#FetchRequest(sortDescriptors: [NSSortDescriptor(keyPath: \Place.name, ascending: true)]) var places: FetchedResults<Foo>
var body: some View {
//...
}
}
struct ActivityDatesView {
#ObservedObject var place: Place
var body: some View {
List(Array(place.activities as Set), id: \.self) { activity in
Text(dateFormatter.string(from: activity.date)) // This displays duplicate entries
}
}
}
struct ActivityView {
#ObservedObject var place: Place
var selectedDate: Date
var body: some View {
//...
}
}

Answer 1

Because to get the features of Set() your struct must be Hashable and Equatable if you customize this protocols and override the default provided functions you get the desired functionality with much less code. The best is all your dates save their time and you dont lose any information.
struct ContentView: View {
let activities = [Activity(date: Date()), Activity(date: Date().addingTimeInterval(3600)), Activity(date: Date().addingTimeInterval(24*3600))]
var body: some View {
NavigationView {
VStack {
List(Array(Set(activities))) { activity in
//prints 2 dates
Text(activity.date.description)
}
}
}
}
}
struct Activity: Equatable, Identifiable, Hashable {
var id = UUID()
var name = "Activity"
var date: Date
//Add this function to your struct
static func == (lhs: Activity, rhs: Activity) -> Bool {
Calendar.current.dateComponents([.year, .month, .day], from: lhs.date) == Calendar.current.dateComponents([.year, .month, .day], from: rhs.date)
}
//Add this function also to your struct
func hash(into hasher: inout Hasher) {
hasher.combine(Calendar.current.dateComponents([.year, .month, .day], from: date))
}
}