From: Robert Klemme <shortcutter@...>
Date: 2010-09-16T15:20:15+09:00
Subject: Re: access super from yield block?

On 15.09.2010 22:12, Gene Angelo wrote:
>> What exactly are trying to achieve?
>
> I have class A that derives from class B
>
> A#parse and A#parse! override members of the same name in B
>
> A#parse and A#parse! both call A#do_parse to retrieve arguments from the
> command line in a loop. A yield in A#do_parse returns the arguments
> (argv). I want to call 'super argv' from both A#parse and A#parse! but
> super is not set to A#super.

What should "super argv" do?  Your description is completele technical 
but you don't tell what the problem is that you are trying to solve here.

> # simplified...
> class A<  B
> ..
>
> def parse
>     do_parse {|a| super a}
> end
>
> def parse!
>     do_parse {|a| super a}
> def

Where's the difference between #parse and #parse!?  Also, why do you 
want to call the superclass method from the block?  This will result in 
parsing input twice, since B#parse will also call do_parse.  This does 
not seem to make much sense

And, btw. reading from stdin from within method #do_parse is not very 
modular.  It might turn out that you want to read input from a file and 
then you need to break this up anyway.

> def do_parse
>     argv = gets.strip.to_a

This will create an Array with a single element.  Is this really what 
you want?

>     return ['-x'] if argv.index '-x'
>     return ['-h'] if argv.empty?
>     yield argv
> end
> protected :do_parse
>
> ..
> end

And: what does the whole picture look like?  Why do you want several 
classes that somehow must behave differently but apparently share the 
same argument parsing code?  I would have expected different classes to 
have different needs for arguments to be parsed and consequently not 
share parsing code.  With OptionParser you could do:

class B
   def parse(argv)
     OptionParser.new do |opts|
       fill opts
     end.parse argv
   end

   def parse!(argv)
     OptionParser.new do |opts|
       fill opts
     end.parse! argv
   end

protected
   def fill(opts)
     opts.on '-x' do |...| end
     opts.on '-y' do |...| end
   end
end

class A < B
   def fill(opts)
     super
     opts.on '-z' do |...| end
   end
end

Cheers

	robert

-- 
remember.guy do |as, often| as.you_can - without end
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