Safely convert Double to Int and take care of overflows. Wont take care of precision for large values. Raw

doubleToInt.swift

func doubleToInt(_ input: Double) -> Int? {
  guard (
    input < Double(Int.max).nextDown &&
    input > Double(Int.min).nextDown)
    else {
    // Int overflow
    return nil
  }


  return Int(input)
}

doubleToInt(Double(Int.max)) // returns nil
doubleToInt(Double(Int.max) - 1535) // returns nil
doubleToInt(Double(Int.max) - 1536) // returns 9223372036854773760

doubleToInt(Double(Int.min)) // -9223372036854775808
doubleToInt(Double(Int.min) - 1) // -9223372036854775808
doubleToInt(Double(Int.min) - 1024) // -9223372036854775808
doubleToInt(Double(Int.min) - 1025) // nil