Sort array of objects by two properties

Question

This has been asked and answered before using NSSortDescriptor where it is quite easy. But is there a Swift-standard way using Array.sort()?

struct Sortable {
 let isPriority: Bool
 let ordering: Int
}

Sorting an array of Sortables by one property is simple:

sort { 0ドル.ordering < 1ドル.ordering }

But I want to sort by isPriority then by ordering - and I can't get my head around a simple statement to make that happen.

• Alexander: Should we close this question as a dupe, and point to this more popular variant of it? stackoverflow.com/q/37603960/3141234

Answer 1

Yes there is a very simple way using the Array.sort()

Code:

var sorted = array.sorted({ (s1, s2) -> Bool in
 if s1.isPriority && !s2.isPriority {
 return true //this will return true: s1 is priority, s2 is not
 }
 if !s1.isPriority && s2.isPriority {
 return false //this will return false: s2 is priority, s1 is not
 }
 if s1.isPriority == s2.isPriority {
 return s1.ordering < s2.ordering //if both save the same priority, then return depending on the ordering value
 }
 return false
})

The sorted array:

true - 10
true - 10
true - 12
true - 12
true - 19
true - 29
false - 16
false - 17
false - 17
false - 17
false - 18

Another a bit shorter solution:

let sorted = array.sorted { t1, t2 in 
 if t1.isPriority == t2.isPriority {
 return t1.ordering < t2.ordering 
 }
 return t1.isPriority && !t2.isPriority 
}

• tobygriffin: This is very good thank you. It can be written more tersely - I will add to your answer.
• tobygriffin: My edit to your answer was rejected, so here is the code I used. let sorted = array.sorted { t1, t2 in if t1.isPriority == t2.isPriority { return t1.ordering < t2.ordering } return t1.isPriority && !t2.isPriority }
• Crashalot: Shouldn't array.sorted be array.sort?
• Dejan Skledar: @Crashalot yeah. But in old swift it was '.sorted'
• Crashalot: @DejanSkledar makes sense, but perhaps an edit is in order for new Swift users?

Answer 2

Here is a simple statement to do this sorting:

var sorted = array.sort { 0ドル.isPriority == 1ドル.isPriority ? 0ドル.ordering < 1ドル.ordering : 0ドル.isPriority && !1ドル.isPriority }

• adamjansch: sort sorts an array in place; you need sorted here, as you're creating a new array.

Answer 3

Conform to Comparable! 😺

extension Sortable: Comparable {
 static func < (sortable0: Sortable, sortable1: Sortable) -> Bool {
 sortable0.isPriority == sortable1.isPriority
 ? sortable0.ordering < sortable1.ordering
 : sortable0.isPriority
 }
}

Which will allow for:

sortableArray.sorted()

Answer 4

I created a blog post on how to this in Swift 3 and keep the code simple and readable.

You can find it here:

http://master-method.com/index.php/2016/11/23/sort-a-sequence-i-e-arrays-of-objects-by-multiple-properties-in-swift-3/

You can also find a GitHub repository with the code here:

https://github.com/jallauca/SortByMultipleFieldsSwift.playground

The gist of it all, say, if you have list of locations, you will be able to do this:

struct Location {
 var city: String
 var county: String
 var state: String
}
var locations: [Location] {
 return [
 Location(city: "Dania Beach", county: "Broward", state: "Florida"),
 Location(city: "Fort Lauderdale", county: "Broward", state: "Florida"),
 Location(city: "Hallandale Beach", county: "Broward", state: "Florida"),
 Location(city: "Delray Beach", county: "Palm Beach", state: "Florida"),
 Location(city: "West Palm Beach", county: "Palm Beach", state: "Florida"),
 Location(city: "Savannah", county: "Chatham", state: "Georgia"),
 Location(city: "Richmond Hill", county: "Bryan", state: "Georgia"),
 Location(city: "St. Marys", county: "Camden", state: "Georgia"),
 Location(city: "Kingsland", county: "Camden", state: "Georgia"),
 ]
}
let sortedLocations =
 locations
 .sorted(by:
 ComparisonResult.flip <<< Location.stateCompare,
 Location.countyCompare,
 Location.cityCompare
 )