From: Jacob Fugal <lukfugl@...>
Date: 2005-09-10T04:46:55+09:00
Subject: Re: Dynamic method execution problem

On 9/9/05, joe.yakich@gmail.com <joe.yakich@gmail.com> wrote:
<snip definition of methods array>
> # The ie variable here refers to a Watir::IE object
> begin
>   my_method = methods.shift
>   puts "Trying #{my_method}"
>   eval "#{my_method}(ie)"
> end
> 
> rescue UnknownObjectException
>   if methods.length > 0
>     retry
>   else
>     raise
>   end

First, a fix... you don't want the end to the begin block until after
the rescue, example:

begin
  # do risky operation
rescue
  # recover from failure
end

Then, translating to use send instead of eval:

begin
  my_method = methods.shift
  puts "Trying #{my_method}"
  send(my_method.to_sym, ie)
rescue UnknownObjectException
  retry unless methods.empty?
  raise
end

(I also changed the content of the rescue clause to something that
flows a bit nicer for me, but this is just a style issue. What you had
works fine)

The send method sends the method identified by the first argument to
the receiver (here the implicit self) with the remainder of the
arguments.

Myself, rather than using retry, I'd do something like this:

methods = [ :method1, :method2, ... ]

methods.find do |method|
  puts "Trying #{method}"
  begin
    send( method, ie )
    method
  rescue
  end
end or raise "No applicable method found"

This makes the nature of looping through the methods more explicit,
rather than relying on a combination of .shift, .empty? and retry.

Jacob Fugal