From: ts <decoux@...>
Date: 2002-06-05T15:23:02+09:00
Subject: Re: eval and local variable

>>>>> "P" == Park Heesob <phasis@hananet.net> writes:

P> eval "foo = 'bar'"
P> p local_variables  #--> ["foo"]
P> p eval "foo"       #--> "bar"
P> p foo     #--> foo.rb:4: undefined local variable or method `foo' for
P> #<Object:0x2ac38ce0> (NameError)

P> Why can't use foo variable directly?

 When ruby compile the script, it find `foo' at this time there is no local
 variable defined (eval is not yet executed) and ruby think that you have
 wanted to write `foo()', i.e. a call to the method #foo

 At runtime, eval will create a local variable, but when ruby execute the
 lines `p foo' it will try to call the method #foo, because this is what it
 has compiled. Here an example

pigeon% cat b.rb
#!/usr/bin/ruby
def foo
   "ruby has called #foo"
end

eval "foo = 'bar'"
p local_variables 
p eval "foo"
p foo
pigeon% 

pigeon% b.rb
["foo"]
"bar"
"ruby has called #foo"
pigeon% 



Guy Decoux