Re: Win32OLE bug

At 10:12 PM 3/11/2004, Chad Fowler wrote:
>On Thursday, March 11, 2004, at 09:02 PM, Kent Sibilev wrote:
>>On Mar 11, 2004, at 7:19 PM, Bret Pettichord wrote:
>>
>>I don't know much about win32ole extension, but LocalJumpError has 
>>nothing to do with the extension, but more with how "return" operation 
>>works in Ruby. For example,
>>
>>$ ruby -v
>>ruby 1.9.0 (2004-03-10) [powerpc-darwin]
>>$ irb
>>irb(main):001:0> (1..10).each{return}
>>LocalJumpError: return from proc-closure
>>         from (irb):1
>>         from (irb):1:in `each'
>>         from (irb):1

Kent, thanks. This helps me see that the behavior i'm seeing is not a 
consequence of win32ole.

>>The thing is that in this case the context of the 'return' has passed 
>>already.
>>For details check out this discussion:
>>http://blade.nagaokaut.ac.jp/cgi-bin/scat.rb/ruby/ruby-core/2583

I'm sorry, but i'm too dumb to understand this. Instead, i made some 
experiments, which i repeat below.

>>>I'm seeing the following in 1.8.0 (mswin32) using win32ole:
>>>
>>>irb(main):009:0> for form in $iec.document.forms
>>>irb(main):010:1> if form.action == "start"
>>>irb(main):011:2> return form
>>>irb(main):012:2> end
>>>irb(main):013:1> end
>>>LocalJumpError: unexpected return
>>>         from (irb):11
>>>         from (irb):9:in `each'
>>>         from (irb):9
>
>Bret,
>
>    There are probably better ways to do this that I would think of if I 
> weren't so tired, but this one will get you around the JumpError problem.
>
>form = callcc do |cc|
>   ie.document.forms.each do |form|
>     if(form.action == "start")
>       cc.call(form)
>     end
>    end
>end
>
>puts form.inspect
>"#<WIN32OLE:0x28bcf48"
>
>
>Chad

Thanks Chad. I actually included my workaround in my original post (but 
which kent snipped). I don't understand what you have here. Here's my 
original workaround:

def get_form_by_action(action)
   "Return the first Form on the current page that has the specified Action."
   retval = nil # this ugliness avoids scripts hanging on exit (1.6) or a 
LocalJumpError (1.8)
   for form in @iec.document.forms
     next if retval
     if form.action == action
       retval = IEDomFormWrapper.new(form)
     end
   end
   return retval
end


Here is what i really want to do:

irb(main):036:0> $iec.document.forms.find {|f| f.action == "start" }
WIN32OLERuntimeError: Unknown property or method : `find'
     HRESULT error code:0x80020006
       Unknown name
         from (irb):36:in `method_missing'
         from (irb):36
         from ?:0

forms is an OLE collection object, so it supports each, but apparently 
doesn't have Enumerable mixed in. Can i mix this in on my own? Should i be 
expecting this to be done by the WIN32OLE library?

Here's my latest rewrite, which works, and is easier for me to understand 
and explain than the one you gave Chad. (I don't know what callcc does. 
Continuations? I'll leave that for another day.)

def get_form_by_action(action)
   "Return the first Form on the current page that has the specified Action."
   for form in @iec.document.forms
     break if form.action == action
   end
   IEDomFormWrapper.new(form)
end

I did try the following, but was surprised to see that it didn't work, 
since i thought that this was supposed to be the same as the previous but 
more the ruby way.

def get_form_by_action(action)
   "Return the first Form on the current page that has the specified Action."
   @iec.document.forms.each do | form |
     break if form.action == action
   end
   IEDomFormWrapper.new(form)
end

This give this error:

irb(main):044:0> get_form_by_action("start")
NameError: undefined local variable or method `form' for #<Object:0x100f9480>
         from ./toolkit/iec-assist.rb:39:in `get_form_by_action'
         from (irb):44
         from ./toolkit/iec-assist.rb:2

To correct, i need to explicitly change the scope of the bound variable:

def get_form_by_action(action)
   "Return the first Form on the current page that has the specified Action."
   form = nil
   @iec.document.forms.each do | form |
     break if form.action == action
   end
   IEDomFormWrapper.new(form)
end

As you may know i am preparing to teach novices to use Ruby, and i can't 
quite think of how i can teach them why these two forms are different. It 
would be much easier for me to be able to say they are the same. (Between 
you and me, i see that the scope of the bound variable is different between 
the for-in and each forms. But this means that the difference is more than 
just syntactic sugar.)

So, am i still confused somewhere? Is it supposed to be this way? (I'm 
using 1.8.0.)

Is there a way i can get forms.find to work directly?

Bret

______________________________________
  Bret Pettichord, Software Tester
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