From: Florian Gross <flgr@...>
Date: 2004-09-30T03:35:05+09:00
Subject: Re: Binding of the Caller (redux)

Gavin Kistner wrote:

> On Sep 28, 2004, at 10:29 AM, Florian Gross wrote:
>> Gavin Kistner wrote:
>>> So does "... trailing statements of method using it aren't in the 
>>> block" mean "you can't place any statements after the 
>>> Binding.of_caller invocation"? (Like it irrevocably changes the 
>>> context and can't get you back to where you were or something?)
>> I tried to make the interface obvious in the documentation (see the 
>> sample), but I seem to have failed. Do you have any suggestions for 
>> how I could fix this?
> Er, to which sample are you referring?

The old one, but it might have been a bit unclear.

I have changed the documentation according to your suggestions, thank 
you. Here's the new documentation:

# This method returns the binding of the method that called your
# method. It will raise an Exception when you're not inside a method.
#
# It's used like this:
#   def inc_counter(amount = 1)
#     Binding.of_caller do |binding|
#       # Create a lambda that will increase the variable 'counter'
#       # in the caller of this method when called.
#       inc = eval("lambda { |arg| counter += arg }", binding)
#       # We can refer to amount from inside this block safely.
#       inc.call(amount)
#     end
#     # No other statements can go here. Put them inside the block.
#   end
#   counter = 0
#   inc_counter(2)
#   counter # => 2
#
# Binding.of_caller must be the last statement in the method.
# This means that you will have to put everything you want to
# do after the call to Binding.of_caller into the block of it.
# This should be no problem however, because Ruby has closures.
# If you don't do this an Exception will be raised. Because of
# the way that Binding.of_caller is implemented it has to be
# done this way.

> - Gavin, who looks forward to a version of Ruby which has a simple 
> "#caller" method that points to the instance which invoked the current 
> method.

Yup, I also think that all this ought to be easier in a future Ruby. 
This is the best I can do for now, unfortunately.

Regards,
Florian Gross