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Swift for Rubyists: Optionals

• nottombrown 12y ago
  Author here. Let me know your thoughts, concerns, and favorite dinosaur.
  • notduncansmith 12y ago
    Nothing to do with the article, but I think it's interesting to see someone else with the "not#{first_name}#{last_name}" pattern. I didn't know that was a common thing.
    • nottombrown 12y ago
      Totally trending. All of us Smiths, Browns, and Johnsons have to do something to claim our handles. http://names.mongabay.com/most_common_surnames.htm http://names.mongabay.com/most_common_surnames.htm
• anorwell 12y ago
  You don't touch on the fact that options act can act Monads (i.e., that you can invoke an operation on the inner value, conditional on whether or not the optional value is present). For example, an optional user translates naturally to an optional user.name. I haven't tried swift, and it's not obvious to me from the swift documentation if their options support arbitrary transformations, or just method chaining. In ruby (with ActiveSupport) this is the difference between: might_be_nil.try(:method) and might_be_nil.try { |value| my_function(value) } The latter is more general and useful than the former.
  • nottombrown 12y ago
    Here's the source of try from active_support def try(*a, &b) if a.empty? && block_given? yield self else public_send(*a, &b) if respond_to?(a.first) end end https://github.com/rails/rails/blob/d68419a88e424e588c2d8decc69874bd00588766/activesupport/lib/active_support/core_ext/object/try.rb https://github.com/rails/rails/blob/d68419a88e424e588c2d8dec... Should be easy to do the same in swift. Let me take a stab at it.
  • nottombrown 12y ago
    Here's an implementation of the latter try operator in swift. extension Optional { func try<U>(f: (T) -> U) -> Optional<U> { if let unwrapped = self { return f(unwrapped) } else { return nil } } } You can see how to use it in this gist: https://gist.github.com/nottombrown/c6585cad9588a9dc5383 https://gist.github.com/nottombrown/c6585cad9588a9dc5383
• deleted 12y ago
  [deleted]
• krisdol 12y ago
  Is this different than setting a default value of nil to user? def print_favorite_dinosaur(user: nil) or def print_favorite_dinosaur(user = nil) Or is it effectively a different syntax for the same concept? In either language, you still signal that the argument could be nil, and you still have to guard against it. Or so I think
  • nottombrown 12y ago
    In Swift, you have to signal and guard against the nil. In ruby, you choose whether to signal and you choose whether to guard. Here are some ruby examples that may be more clear: Does not signal user = User.find_by_favorite_dinosaur("Dromiceiomimus") Does not guard def print_favorite_dinosaur(user) p "User's favorite dinosaur is #{user.dino})" end Signals and guards def print_favorite_dinosaur(user) if user p "User's favorite dinosaur is #{user.dino})" else p "No user. (Let's assume she likes T-rexs)" end end possible_user = User.find_by_favorite_dinosaur("Dromiceiomimus") print_favorite_dinosaur(possible_user)
    • krisdol 12y ago
      Thanks, I didn't know that swift requires the optional to be guarded against.