Eval bind

Ruby
1

How should I call eval from member function that binds to global
context?
Something like

$binding = binding
class InterpreterCallback
def methods(expr)
begin
return eval(expr, $binding).class.instance_methods(false).sort
rescue ScriptError, StandardError
printf “ERR: %s\n”, $! || ‘exception raised’
return []
end
end
end

but this does not work when I am calling InterpreterCallback::methods
from C++ (for example when new local variable in the global context is
created).

Also I do not understand following

This code:

puts eval(“var” ).class
puts eval(“var”).class.instance_methods(false).sort
var = “”;

produces:

NilClass
&
^
inspect
nil?
to_a
to_f
to_i
to_s
|

and this code

puts eval(“var” ).class
puts eval(“var”).class.instance_methods(false).sort

produces

undefined local variable or method `var’ for main:Object (NameError)

which is exactly what I would expect in the first case also.

Thank you

2

On 7/30/06, Karel M. [email protected] wrote:

How should I call eval from member function that binds to global context?

There is the TOPLEVEL_BINDING, although I don’t if it will help you.

J.

3

On Sun, Jul 30, 2006 at 07:44:06PM +0900, Karel M. wrote:

This code:

puts eval(“var” ).class
puts eval(“var”).class.instance_methods(false).sort
var = “”;

produces:

NilClass
[…]
which is exactly what I would expect in the first case also.
When the “var” String is eval()ed, var="" has already been parsed. Ruby
already knows that var refers to a local variable, so “var” will be
interpreted correspondingly. When this happens, var hasn’t been assigned
to,
though, so the returned value is nil.

This is what’s happening:

eval(“a”) # => nil
a = 1 # since the parser has seen this, “a” will be a local
# in code parsed from now on. Its value is nil until it is
# initialized.

Compare it to the following situation, where the block is parsed before
you
assign to a:

instance_eval { a } # =>
a = nil

~> -:1: undefined local variable or method `a’ for main:Object

(NameError)

~> from -:1

4

J.

That works great. Thanks