How to convert a decimal number to binary in Swift?

You can convert the decimal value to a human-readable binary representation using the String initializer that takes a radix parameter:

let num = 22
let str = String(num, radix: 2)
print(str) // prints "10110"

If you wanted to, you could also pad it with any number of zeroes pretty easily as well:

Swift 5

func pad(string : String, toSize: Int) -> String {
  var padded = string
  for _ in 0..<(toSize - string.count) {
    padded = "0" + padded
  }
    return padded
}

let num = 22
let str = String(num, radix: 2)
print(str) // 10110
pad(string: str, toSize: 8)  // 00010110