Custom pipe operator to conditionally call a method if optional is present

optional_pipe.swift

infix operator |?

func |?<I,O>(left: I?, pipeFunc: ((I) -> O?)) -> O? {
  guard let value = left else { return nil }
  return pipeFunc(value)
}

let formatter = DateFormatter()
formatter.locale = Locale(identifier: "en_US_POSIX")
formatter.timeZone = NSTimeZone.local
formatter.dateFormat = "MM/dd/yyyy"

func convertToDate(_ str: String) -> Date? {
  return formatter.date(from: str)
}

var birthday: String? = "9/14/2020"
let result: Date? = birthday |? { return convertToDate($0) }
let mapResult: Date?? = birthday.map { return convertToDate($0) }
let flatMapResult: Date? = birthday.flatMap { return convertToDate($0) }