Filtering an array

FilteredArray.playground

import UIKit

struct AStruct {
  let anInt: Int
  let aString: String
}

var array: [AStruct]

array = [AStruct(anInt: 10, aString: "foo"),
         AStruct(anInt: 10, aString: "bar"),
         AStruct(anInt: 10, aString: "foobar"),
         AStruct(anInt: 1, aString: "apple"),
         AStruct(anInt: 1, aString: "orange"),
         AStruct(anInt: 1, aString: "grape"),
         AStruct(anInt: 2, aString: "Bob"),
         AStruct(anInt: 2, aString: "Carol"),
         AStruct(anInt: 2, aString: "Ted"),
         AStruct(anInt: 2, aString: "Alice"),
         AStruct(anInt: 3, aString: "talc"),
         AStruct(anInt: 3, aString: "quartz"),
         AStruct(anInt: 3, aString: "carborundum"),
]

var intSet = Set<Int>()
let filtered = array.filter{thisStruct in
  let theInt = thisStruct.anInt
  if intSet.contains(theInt) {
    return false
  } else {
    intSet.insert(theInt)
    return true
  }
}

filtered.forEach{print($0)}

The above code filters the array array to get rid of entries that have the same value for anInt. The first entry for any given anInt value is preserved in the filtered array.

The output is:

AStruct(anInt: 10, aString: "foo")
AStruct(anInt: 1, aString: "apple")
AStruct(anInt: 2, aString: "Bob")
AStruct(anInt: 3, aString: "talc")