From: Josh Cheek <josh.cheek@...>
Date: 2010-12-02T01:27:04+09:00
Subject: Re: Cutting down on logging statements

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On Wed, Dec 1, 2010 at 8:48 AM, Iain Barnett <iainspeed@gmail.com> wrote:

> Hi,
>
> As hacky ideas go, how does this sound? My code is peppered with logging
> statements which I'd rather not wade through, so maybe I could define all my
> methods with a leading underscore but call them without e.g.
>
> def _my_method...
>
> @n = my_method @a, @b, @c ...
>
> and use method missing to wrap all the calls with logging and then remove
> the underscore and recall the method.
>
> I tried using the Aquarius lib but it didn't work for me, so this is my
> crazy idea for the day. Aside from putting all my money into buying
> government debt.
>
> Is it crazy?
>
> Regards,
> Iain
>
>
I'm not especially keen on method_missing, it seems difficult to diagnose
when it has issues, and I always worry about it colliding with other
method_missings. It would also mean you'd have to hack respond_to as well
(if you want to play nice, anyway). And it means you can't override methods,
for example:

class MyClass
  def _foo(arg)
  end
  def _to_s
    "you will never see me"
  end
  def method_missing(meth,*args,&block)
    if respond_to?("_#{meth}")
      puts "LOGGING: '#{meth}' RECEIVED #{args.inspect} WITH#{'OUT' unless
block} A BLOCK"
    else
      super
    end
  end
end

m = MyClass.new
m.foo(:bar) { }
puts m.to_s

# >> LOGGING: 'foo' RECEIVED [:bar] WITH A BLOCK
# >> #<MyClass:0x0000010086ca80>






Here is a different way, which allows you to exert a bit more control. Note
that this won't work on 1.8.6. Some other things you could do would be to
have it hook into a callback so you can customize the logging for each
class, or even each method that uses it; or to allow additional args to
loggable method, which would then be the custom message (ie priority and
message).

alias :log :puts

module Loggable

  def loggable( meth , &block )
    define_actual    meth , &block
    define_loggable  meth
  end

  def define_actual( meth , &block )
    define_method "_#{meth}" , &block
  end

  def define_loggable(meth)
    define_method meth do |*args,&block|
      log "LOGGING: '#{meth}' RECEIVED #{args.inspect} WITH#{'OUT' unless
block} A BLOCK"
      send "_#{meth}" , *args , &block
    end
  end

end


class BreadBox

  extend Loggable

  def initialize
    @slices = 0
  end

  # a logging method
  loggable :insert do |n|
    @slices += n
  end

  # a non-logging method
  def remove(n)
    @slices -= n
  end

  # can log overridden methods
  loggable :to_s do
    "<BreadBox slices=#{@slices}>"
  end

end

box = BreadBox.new
BreadBox.instance_methods(false)  # => [:_insert, :insert, :remove, :_to_s,
:to_s]
box.respond_to? :insert           # => true
box.insert 5                      # => 5
box.remove 3                      # => 2
box.insert 7                      # => 9
box.to_s                          # => "<BreadBox slices=9>"

# >> LOGGING: 'insert' RECEIVED [5] WITHOUT A BLOCK
# >> LOGGING: 'insert' RECEIVED [7] WITHOUT A BLOCK
# >> LOGGING: 'to_s' RECEIVED [] WITHOUT A BLOCK

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