How to find object with smallest property value in a Swift object array?

Question

I have the following Object Array for the Place class:

class Place: NSObject {
    var distance:Double = Double()
    init(_ distance: Double) {
        self.distance = distance
    }
}


let places = [Place(1.5), Place(8.4), Place(4.5)]

I need to get the Place with the minimum distance. I tried using

let leastDistancePlace = places.min { $0.distance > $1.distance }

as per this answer for a similar question, but it gave the following error.

Contextual closure type '(Place) -> _' expects 1 argument, but 2 were used in closure body

PS:

As per @robmayoff 's answer, I tried the following in a playground, but I keep getting an error:

value of Type [Place] no member min

Please check this screenshot.

My swift version is : Apple Swift version 2.2 (swiftlang-703.0.18.8 clang-703.0.31)

You should use max or min (as in the referenced answer), not map — Martin R
– Martin R, Commented Mar 24, 2017 at 18:23
“it does not work” is not enough information. How does it fail? Do you get a compile-time error? Do you get a run-time error? Does it compile and run but produce the wrong answer? Please edit your question to include these details. — rob mayoff
– rob mayoff, Commented Mar 24, 2017 at 18:27
Incidentally, in your attempt, you said places.map but the answer you linked said places.max. Perhaps you meant to say places.min? — rob mayoff
– rob mayoff, Commented Mar 24, 2017 at 18:28
Why do you leave a comment at the referenced answer that "it should be map" and then ask a new question that "map does not work"? — Martin R
– Martin R, Commented Mar 24, 2017 at 18:28
I have copied your updated code into a new Xcode 8.2.1/Swift 3 project and it compiles (and runs) without problems. — Martin R
– Martin R, Commented Mar 24, 2017 at 18:50

rob mayoff · Accepted Answer · 2017-03-24 18:42:25Z

18

let leastDistancePlace = places.min { $0.distance < $1.distance }

or

let leastDistancePlace = places.min(by: { $0.distance < $1.distance })

Example:

:; xcrun swift
"crashlog" and "save_crashlog" command installed, use the "--help" option for detailed help
Welcome to Apple Swift version 3.0.2 (swiftlang-800.0.63 clang-800.0.42.1). Type :help for assistance.
  1>     class Place { 
  2.         var distance:Double = Double() 
  3.         init(_ distance: Double) { 
  4.             self.distance = distance 
  5.         } 
  6.     } 
  7.  
  8.  
  9.     let places = [Place(1.5), Place(8.4), Place(4.5)] 
 10.     let leastDistancePlace = places.min { $0.distance < $1.distance }
places: [Place] = 3 values {
  [0] = {
    distance = 1.5
  }
  [1] = {
    distance = 8.4000000000000004
  }
  [2] = {
    distance = 4.5
  }
}
leastDistancePlace: Place? = (distance = 1.5) {
  distance = 1.5
}
 11>

answered Mar 24, 2017 at 18:42

rob mayoff

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2 Comments

toing_toing Over a year ago

please check the updated question. Its quite bizzare. I believe your solution should work, but it doesn't.

vacawama Over a year ago

@toing_toing, use minElement instead of min in Swift 2.2. You really should update to Swift 3 and latest Xcode.

Daivest · Accepted Answer · 2017-03-24 18:26:52Z

1

let sortedPlaces = places.sorted(by: { $0.distance < $1.distance })
let first = sortedPlace.first

just use sort

answered Mar 24, 2017 at 18:26

Daivest

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3 Comments

Martin R Over a year ago

If you only need the the smallest (or largest) element then max/min is more efficient than sorting the array.

Hamish Over a year ago

Or min(by:). O(n) rather than O(nlog(n)).

Daivest Over a year ago

oh, my bad, forgot about min =)

jnewkirk · Accepted Answer · 2017-03-24 18:31:45Z

1

Your question is poorly worded however I think I know what you are trying to ask. The mapping function is generally used for tranformations:

let distances = places.map({ (place: Place) -> Int in
    place.distance
})

For shorthand

let distances = places.map({ $0.distance })

You can then use max or min on this array of integers in order to extract the value you desire.

answered Mar 24, 2017 at 18:31

jnewkirk

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