From: Adam Fields <rubylist09813240987@...>
Date: 2004-07-17T06:08:09+09:00
Subject: Re: Dynamically replacing methods for efficiency

On Sat, Jul 17, 2004 at 05:57:14AM +0900, Florian Gross wrote:
> Hal Fulton wrote:
> 
> >For example, I'll name this method "action"; suppose that in
> >general, it just calls do_this and do_that.
> >
> >  def action
> >    do_this
> >    do_that
> >  end
> >
> >But now suppose we enable things like a debug mode and a
> >trace mode and logging and a configurable delay and such:
> >
> >  def action
> >    STDERR.puts "Entering action" if @trace
> >    STDERR.puts "before do_this: foo = #@foo" if @debug
> >    @log.puts "#{Time.now}: Useful info" if @log
> >    sleep(@delay) if @delay
> >    do_this
> >    STDERR.puts "Returned from do_this" if @trace
> >    STDERR.puts "after do_this: foo = #@foo" if @debug
> >    @log.puts "#{Time.now}: More useful info" if @log
> >    do_that
> >    STDERR.puts "Returned from do_that" if @trace
> >    STDERR.puts "after do_that: foo = #@foo" if @debug
> >    @log.puts "#{Time.now}: Still more useful info" if @log
> >  end
> >
> >Here we've added ten if-statements. If #action is called
> >frequently, performance will degrade even if these special
> >attributes are not set.
> 
> Maybe something like this will work reasonably?
> 
>   def initialize
>     @action_hooks = Hash.new do |hash, method|
>       hash[method] = Hash.new do |type_hash, type|
>         type_hash[type] = Array.new
>       end
>     end
>   end
> 
>   def call_hook(method, type, *more)
>     @action_hooks[method][type].each { |hook| hook.call(*more) }
>   end
> 
>   def register_hook(method, type, &block)
>     @action_hooks[method][type] << block
>   end
> 
>   def action
>     call_hook(:action, :before_do_this)
>     do_this
>     call_hook(:action, :before_do_that)
>     do_that
>     call_hook(:action, :before_end)
>   end
> 
> I suppose that someway it could be factored out to a reusable Mix-In.

I'm totally new to ruby, but it seems like blocks are the right way to
go for this.

Maybe something like this:

---------------------------------------------------------

def do_this
  print "this" + "\n"
end

def do_that
  print "that" + "\n"
end

def hook
  yield
end

action = "trace"
def hook
  print "hooked" + "\n"
  yield
end if action == "trace"

hook {do_this}
hook {do_that}


-- 
				- Adam

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