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.ordering < $1.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.

Should we close this question as a dupe, and point to this more popular variant of it? stackoverflow.com/q/37603960/3141234 — Alexander
– Alexander, Commented Sep 27, 2023 at 17:17

Dejan Skledar · Accepted Answer · 2017-10-15 08:50:08Z

64

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 
}

edited Oct 15, 2017 at 8:50

user1951992

answered Apr 9, 2015 at 6:31

Dejan Skledar

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7 Comments

tobygriffin Over a year ago

This is very good thank you. It can be written more tersely - I will add to your answer.

tobygriffin Over a year ago

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 Over a year ago

Shouldn't array.sorted be array.sort?

Dejan Skledar Over a year ago

@Crashalot yeah. But in old swift it was '.sorted'

Crashalot Over a year ago

@DejanSkledar makes sense, but perhaps an edit is in order for new Swift users?

|

John · Accepted Answer · 2016-05-14 06:18:48Z

17

Here is a simple statement to do this sorting:

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

answered May 14, 2016 at 6:18

John

1,8263 gold badges18 silver badges18 bronze badges

1 Comment

adamjansch Apr 24 at 15:01

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

user652038 · Accepted Answer · 2020-03-13 05:32:50Z

2

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()

answered Mar 13, 2020 at 5:32

user652038

Comments

Jaime Allauca · Accepted Answer · 2016-11-23 21:16:31Z

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
        )

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