FP-benefit.swift

struct User {
	let name: String?
	let surname: String?
	let nickname: String?	
}

//Our goal is to build a human-readable string in a: 
//Name Surname, "Nickname" 
//format. 
//The example output would be: 
//Jakub Turek, "Brogrammer"

//---------------------------------------------------
//Non functional approach
//It is very probable to put some bug
extension User {
  var readableName: String {
    if let name = name, let surname = surname, let nickname = nickname, !name.isEmpty, !surname.isEmpty, !nickname.isEmpty {
      return "\(name) \(surname), \"\(nickname)\""
    } else if let name = name, let surname = surname, !name.isEmpty, !surname.isEmpty {
      return "\(name) \(surname)"
    } else if let name = name, let nickname = nickname, !name.isEmpty, !nickname.isEmpty {
      return "\(name), \"\(nickname)\""
    } else if let name = name, !name.isEmpty {
      return name
    } else if let surname = surname, let nickname = nickname, !surname.isEmpty, !nickname.isEmpty {
      return "\(surname), \"\(nickname)\""
    } else if let surname = surname, !surname.isEmpty {
      return surname
    } else if let nickname = nickname, !nickname.isEmpty {
      return "\"\(nickname)\""
    } else {
      return ""
    }
  }
}

//---------------------------------------------------
//Functional Approach
extension Sequence where Iterator.Element == Optional<String> {
  func joinedNonBlanks(separator: String) -> String {
    return self
      .flatMap { $0 }
      .filter { !$0.isEmpty }
      .joined(separator: separator)
  }
}

extension User {
  var fullName: String {
    return [name, surname].joinedNonBlanks(separator: " ")
  }
}

extension User {
  var formattedNickname: String? {
    return nickname.flatMap { !$0.isEmpty ? "\"\($0)\"" : nil }
  }
}

extension User {
  var presentedFullName: String {
    return [fullName, formattedNickname].joinedNonBlanks(separator: ", ")
  }
}
//---------------------------------------------------
//Usage:
User(name: nil, surname: "", nickname: "Brogrammer").presentedFullName == "\"Brogrammer\""
User(name: "Jakub", surname: "", nickname: "Brogrammer").presentedFullName == "Jakub, \"Brogrammer\""