Obtaining number of block parameters

Question

I need to obtain the number of parameters a given block takes. For example:

foobar(1,2,3) { |a, b, c|
}

def foobar(x, y, z, &block)
  # need to obtain numbe         


        

Answer 1

When you materialize a block with &, it becomes a Proc object, which has an arity method. Just be careful - it returns the one's complement if the proc takes a *splat arg.

def foobar(x, y, z, &block)
  p block.arity
end

(Answer via "The Ruby Programming Language" book.)