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Comment by krisdol | Hacker News Reader

Is this different than setting a default value of nil to user?

    def print_favorite_dinosaur(user: nil)

    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

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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)

Thanks, I didn't know that swift requires the optional to be guarded against.

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