CODEWITHSUNDEEP
iosswiftnssortdescriptor
Jack
Jack

Reputation: 14349

What is advantage of NSSortDescriptor over swift High order function?

Below is example use of NSSortDescriptor which gives same result as sortedByFirstNameSwifty then whats need of NSSortDescriptor in Swift ?

class Person: NSObject {
    let firstName: String
    let lastName: String
    let age: Int

    init(firstName: String, lastName: String, age: Int) {
        self.firstName = firstName
        self.lastName = lastName
        self.age = age
    }
    override var description: String {
        return "\(firstName) \(lastName)"
    }
 }

let a = Person(firstName: "a", lastName: "b", age: 24)
let b = Person(firstName: "c", lastName: "d", age: 27)
let c = Person(firstName: "e", lastName: "f", age: 33)
let d = Person(firstName: "g", lastName: "h", age: 31)
let peopleObject = [d, b, a, c]
//SWIFTY
let sortedByFirstNameSwifty =  peopleObject.sorted(by: { $0.firstName < $1.firstName })
print(sortedByFirstNameSwifty)//prints[a b, c d, e f, g h]


//Objective c way
let firstNameSortDescriptor = NSSortDescriptor(key: "firstName", ascending: true, selector: #selector(NSString.localizedStandardCompare(_:)))
let sortedByFirstName = (peopleObject as NSArray).sortedArray(using: [firstNameSortDescriptor])
print(sortedByFirstName)//prints [a b, c d, e f, g h]

Upvotes: 0

Views: 232

Answers (1)

Charles Srstka
Charles Srstka

Reputation: 17060

The advantage of NSSortDescriptor is that you can sort using an array of them, and if two objects turn out to be equal according to the first descriptor, you can then fall back on the second descriptor to sort them.

For example, say you were sorting a number of files by modification date. In the event that two files happen to have exactly the same modification date, you might want to sort those two files by name instead. So you would use an array of sort descriptors, the first of which sorts by date and the second of which sorts by filename.

Upvotes: 5

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