swift 3 - remove objects from array that exist in another array

Question

I have an array with Contact objects inside.

Then I have another array with Users.

class Contact: NSObject {
 var name: String?
 var phoneNumber: String?
 var phoneNumberFormatted: String?
 init(name: String, phoneNumber: String?, phoneNumberFormatted: String) {
 self.name = name
 self.phoneNumber = phoneNumber
 self.phoneNumberFormatted = phoneNumberFormatted
 }
}
 class User: NSObject {
 var name: String?
 }

How can I remove a Contact object from the [Contact] if I have a User in my [User] with a matching name?

I know how to do it through loops but what is most efficient way?

• Walker: I changed the phoneNumber objects name to Contact. Thanks for your help @AlexanderMomchliov
• Leo Dabus: @Walker Is there any reason to make it a NSObject? Otherwise you shouldn't. Also if the fields are required you should use let, make it non optional and add a required initializer for the property(ies)
• Leo Dabus: If you are not going to make your class NSCoding compliant you don't need to subclass NSObject
• Leo Dabus: You are coding in Swift, no need to subclass NSObject unless you have a specific reason (to behave as NSObject)
• Leo Dabus: If you need an instance where it is needed you can take a look at this answer stackoverflow.com/a/37983027/2303865

Answer 1

The best (most computationally efficient) way to do this for non-trivial array sizes is to precompute a set from the array you need to repeatedly search, and filter your other array, keeping elements only if they're not found in the set.

This leverages the O(1) lookup performance of Set. The algorithm as a whole is O(userPhoneNumbers.count + contacts.count)

let userPhoneNumbers = Set(users.lazy.map{ 0ドル.phoneNumber })
let filteredContacts = self.contacts.filter{ !userPhoneNumbers.contains(0ドル.phoneNumber) }

• Walker: Alex, I'm trying to filter by a property that the objects in both arrays have. The answer is not clear to me. Mind expanding a bit? Thanks man
• Alexander: Are you familiar with map/reduce/filter?