Ruby blocks parameter names

Question

Hello,

Does anyone know if there is a way to access the names of the parameters passed in ruby blocks?

E.g.

def do_something()
  # method uses the names of the parameters passed to the block
  # in addition to their values
  # e.g. the strings "i" and "j"
end

do_something { |i, j| ... }

It's a requirement for a dsl I'm writing, and quite an unusual use case. This is probably possible with something like parsetree, I just wondered if there was an easier/cheekier way.

Thanks

Answer 1

update: It looks like Ruby 1.9 can do what you're requesting. See Florian's answer.

Yes, well, Ruby has this great facility for passing named parameters: Hash.

Here's how it works:

def do_something(params)
  params.each do |key, value|
    puts "received parameter #{key} with value #{value}"
  end
end

do_something(:i => 1, :j => 2)

Otherwise, no there's not really a way to get the names of passed variables in Ruby. A variable in Ruby is just a reference to an Object, so there's no way to know from the Object which reference (of the potentially many references) was used in the method call.

Answer 2

This is actually possible, but only in the trunk version of 1.9:

->(a,b,c) {}.parameters

It is not released though and will most probably be included in Ruby 1.9.2.

Regards, Florian Gilcher