how to eval / constantize a string to a method, then pass arguments to it

Question

Given:

s = "foo_bar_path"

How can I eval or constantize s, and pass arguments to it, such as my final result would be the equivalent of:

foo_bar_path(@myvar, @foobar)

I was trying eval(s).send but that doesn't seem to work. And constantize seems to only work on Classes?

Answer 1

You would just use the send method (or public_send depending on your needs) on the appropriate object:

some_object.send(s, @myvar, @foobar)

or if you want to call a method on yourself:

self.send(s, @myvar, @foobar)

The documentation says "symbol" but send is just as happy to get the method name in a string.

Answer 2

Another way to go about this sort of this sort of thing (better for OpenStruct):

#for more in this domain, see the Ruby core API for the Object class
class Demo
  def initialize(n)
    @iv = n
  end
  def hello()
    "Hello, @iv = #{@iv}"
  end
end

k = Demo.new(99)
m = k.method(:hello)
m.call   #=> "Hello, @iv = 99"