From: John Sikora <john.sikora@...>
Date: 2009-09-04T06:03:20+09:00
Subject: Is Passing a Binding with Parameters Possible?

Does anyone know how to pass a binding using parameters instead of a
code block? Is it even possible?

For various reasons (primarily syntactic sugar implementation), I need
to eval a string in one method in the scope of another method. The
following is a  simplified version of the code (which works):


def called_method(*parameters, &code_block)  # code_block handler
ignored.
  parameters.each do |parameter|
    eval(parameter, code_block.binding)
  end
end

def calling_method
  a = 3
  string_to_evaluate = 'puts a'
  called_method(string_to_evaluate){}
end

calling_method       # => 3


Obviuosly, this requires a code block for 'called_method'. In the actual
code, whenever eval is used, parameters are always present. Code blocks
are optional. So when a code block is not needed, the empty code block
has to be included.

No big deal, but it would be nice to be able to use the parameters to
pass the binding (since they are always present when eval is used). Such
as:


def called_method(*parameters, &code_block)  # code_block handler
ignored.
  parameters.each do |parameter|
    eval(parameter, parameters.binding)
  end
end

def calling_method
  a = 3
  string_to_evaluate = 'puts a'
  called_method(string_to_evaluate)
end

calling_method      # => in 'called_method' private method 'binding'
called...


So I guess .binding is a private method for objects other than code
blocks, in this case an Array. If I change 'parameters.binding' to
'binding', it (of course) does not give the right binding, resulting in
variable 'a' being undefined. I have tried some other code snippets that
I thought might work, but to no avail.

I know a binding could be created inside of calling_method and it could
be could be passed, but the way it is now with the empty braces is
easier, which is the point of syntactic sugar.

Can it be made even easier by passing the binding 'automatically' with
the parameters instead of a code block?

John S.
-- 
Posted via http://www.ruby-forum.com/.