ruby on rails block sytax using &:

Question

So say I have a Question model and an Answer model and Question has_many Answers (it's a multiple choice question).

Suppose that questions is a collection of Question objects.

In order to collect all the answers I can do this:

questions.collect(&:answers)

Two questions:

1. What precisely does this syntax mean? Does it expand to

   questions.collect { |q| q.answers } 
   

   or is there something else going on here?

2. Is there a way to do

   questions.collect { |q| q.answers.shuffle } 
   

   using the same syntax?

   collect(&:answers.shuffle) 
   

   isn't doing it.

I can't seem to find this in tutorials on ruby blocks on the web and searching for it doesn't work (search engines ignore "&:"). I found it in some inherited code.

Thanks

Answer 1

Yes, the first question is N-duplicated, but regarding the second: no, you cannot chain methods. However, nothing stops you -other than writing code that may puzzle people- to create your own tool:

class Symbol
  def to_proc
    proc do |obj| 
      self.to_s.split(/\./).inject(obj, :send)
    end
  end
end

p ["1", "2", "3"].map(&:"to_i.succ")
# [2, 3, 4]

You can even find ways to send arguments, though it won't probably be very beautiful.