Simple code methods for writing closures that don’t have a name in Swift

I thought about closures without names to get odd numbers. There are four simple code methods. Let’s make it progressively simpler.

1st

It’s a complicated but basic way of writing.

var numbers = [22, 21, 9, 14]

let response1 = numbers.compactMap({(number: Int) -> Int? in 
  if (number % 2) != 0 {
    return number
  }
  else {
    return nil
  }
})

2nd

Use number instead of (number: Int) -> Int?.

var numbers = [22, 21, 9, 14]

let response2 = numbers.compactMap({number in 
  if (number % 2) != 0 {
    return number
  }
  else {
    return nil
  }
})

3rd

Remove number and use $0 instead of number.

var numbers = [22, 21, 9, 14]

let response3 = numbers.compactMap({
  if ($0 % 2) != 0 {
    return $0
  }
  else {
    return nil
  }
})

4th

It’s the simplest way. remove ().

var numbers = [22, 21, 9, 14]

let response4 = numbers.compactMap {
  if ($0 % 2) != 0 {
    return $0
  }
  else {
    return nil
  }
}

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