Binary search object - Swift

binary_search.swift

// recursive
func binarySearch<T>(key: Int, arr: [T], range: Range<Int>? = nil, _ callBack: (T) -> Int) -> Int? {
  var rangeDefault: Range<Int>
  if let r = range {
    rangeDefault = r
  } else {
    rangeDefault = 0..<arr.count
  }
  if rangeDefault.lowerBound >= rangeDefault.upperBound {
    return nil
  }
  let indexMid = rangeDefault.lowerBound + (rangeDefault.upperBound - rangeDefault.lowerBound) / 2
  let object = callBack(arr[indexMid])

  if object < key {
    return binarySearch(key: key, 
                        arr: arr, 
                        range: (indexMid + 1)..<rangeDefault.upperBound,
                        callBack)
  } else if object > key {
    return binarySearch(key: key, 
                        arr: arr, 
                        range: rangeDefault.lowerBound..<indexMid,
                        callBack)
  } else {
    return indexMid
  }
}

How to use ?

class A {
  var id: Int
  init(_ id: Int) {
    self.id = id
  }
}
let arr = [
  A.init(0),
  A.init(1),
  A.init(2),
  A.init(3),
  A.init(4),
  A.init(5),
  A.init(6),
]

if let result = binarySearch(key: 6, arr: arr, { item in return item.id}) {
  print(arr[result].id) // 6
}