Putting it all together

To reinforce what we have learned in this chapter, let's look at one more example. For this example, we will create a function that will test to see whether a string value contains a valid IPv4 address. An IPv4 address is the address assigned to a computer that uses the Internet Protocol (IP) to communicate. An IP address consists of four numeric values that range from 0-255, separated by a dot (period). The following is the code example of a valid IP address, that is, 10.0.1.250:

func isValidIP(ipAddr: String?) ->Bool { 
 
  guard let ipAddr = ipAddr else {  
    return false 
  } 
  let octets = ipAddr.split { $0 == "."}.map{String($0)}  
  guard octets.count == 4 else { 
    return false 
  } 
  for octet in octets { 
    guard validOctet(octet: octet) else {  
      return false 
    } 
  } 
  return true 
} 

Since the sole parameter...