Swift slow performance when filtering array

Question

I have an array of a Category class that has a name and parentName. I have a search bar to allow users search for categories by the category name or parentName. My full array has about 600 items. On typing the first letter it takes about 2-3 seconds and freezes all other input on the keyboard. After the first letter everything is fast.

Here is how I am filtering

return self.userData.categories.filter({$0.name.lowercased().hasPrefix(searchText.lowercased()) || ($0.parentName != nil && $0.parentName!.lowercased().hasPrefix(searchText.lowercased()))})

One piece I think it may be is SwiftUI rendering all of the rows, however the initial render is fast.

This is how I render the categories.

List(categories) { category in
    CategoryPickerRowView(category: category, isSelected: category.id == self.transaction.categoryId)
        .onTapGesture { self.transaction.categoryId = category.id }
}

Update: I noticed when the first letter is typed or deleted (when it is slow) I get this message in the logs

[Snapshotting] Snapshotting a view (0x7fb6bd4b8080, _UIReplicantView) that has not been rendered at least once requires afterScreenUpdates:YES.

Can you try filtering in a diff thread? This should avoid freezing i guess — Cerlin
– Cerlin, Commented Jan 30, 2020 at 5:57

Josh Homann · Accepted Answer · 2020-01-30 06:32:37Z

You can use Combine to debounce your search so it happens only after the user stops typing. You can also use Combine to move your filter to the background and then move your assign back to the main queue.

class Model: ObservableObject {
  @Published var searchResults: [String] = []
  let searchTermSubject = CurrentValueSubject<String, Never>("")
  let categorySubject = CurrentValueSubject<String, Never>("")
  private var subscriptions = Set<AnyCancellable>()
  init() {
    Publishers
      .CombineLatest(
        searchTermSubject
          .debounce(for: .milliseconds(250), scheduler: RunLoop.main),
        categorySubject
      )
      .receive(on: DispatchQueue.global(qos: .userInteractive))
      .map { combined -> [String] in
        // Do search here
      }
      .receive(on: RunLoop.main)
      .assign(to: \.searchResults, on: self)
      .store(in: &subscriptions)
  }
}

Michael St Clair · Accepted Answer · 2020-02-12 04:49:38Z

1

By adding .id(UUID()) to the list it fixes the problem.

List(categories) { category in
    CategoryPickerRowView(category: category, isSelected: category.id == self.transaction.categoryId)
        .onTapGesture { self.transaction.categoryId = category.id }
}.id(UUID())

Description found here: https://www.hackingwithswift.com/articles/210/how-to-fix-slow-list-updates-in-swiftui

answered Feb 12, 2020 at 4:49

Michael St Clair

6,73511 gold badges53 silver badges77 bronze badges

Comments

Shashank · Accepted Answer · 2020-01-30 06:03:17Z

-1

Use textfield delegate : -

func textField(_ textField: UITextField, shouldChangeCharactersIn range: NSRange, replacementString string: String) -> Bool
    {
if string.isEmpty
        {
            search = String(search.dropLast())
}else{
      search=textField.text!+string
}

and use ".contain" to search name. eg: -

var search:String = ""
var searchData:NSArray?

let filtered = rewardArray?.filter { ($0.name .lowercased()).contains(search.lowercased()) }


searchData = filtered as NSArray?

and reload your collection or table with searchData

answered Jan 30, 2020 at 6:03

Shashank

211 bronze badge

Collectives™ on Stack Overflow

Swift slow performance when filtering array

3 Answers 3

Comments

Comments

Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

3 Answers 3

Comments

Comments

Comments

Your Answer

Sign up or log in

Post as a guest

Related