From: Robert Dober <robert.dober@...>
Date: 2007-04-19T20:18:52+09:00
Subject: Re: to_s mixin/reflection/newbie stuff

On 4/18/07, hemant <gethemant@gmail.com> wrote:
> On 4/19/07, hemant <gethemant@gmail.com> wrote:
> > On 4/19/07, hemant <gethemant@gmail.com> wrote:
> > > On 4/19/07, Kris Helenek <khelenek@hotmail.com> wrote:
> > > > Thanks Hemant!  I still have trouble seeing things as methods without
> > > > the parentheses(); but it makes perfect sense now.  And i wrote a nice
> > > > little module to duplicate what is often done to create good debug
> > > > output in hibernate (j2ee world):
> > > >
> > > > module ReflectionToString
> > > >   def to_s
> > > >     str = self.class.name + "["
> > > >     for attribute in self.attributes
> > > >       str += attribute[0].to_s + ": " + attribute[1].to_s + ", "
> > > >     end
> > > >     str += "]"
> > > >     str
> > > >   end
> > > > end
> > > >
> > > > Someone could probably clean it up a bit but its just a first pass...
> > >
> > > def to_s
> > >   str = "#{self.class} ["
> > >   @attributes.each {|x| str << "#{attribute[0]}  : #{attribute[1]} , " }
> > >   str << "]"
> > > end
> > >
> > > No need to return str, because last statement evaluated is returned.
> > >
> > > >
> > > > I have a Rails specific question (i know this is kinda the wrong forum,
> > > > but I'm already here..) Where is the appropriate place to store this
> > > > module? In the helper or model folder? lib? A new folder? Don't know the
> > > > conventions yet and I haven't seen anything about utility classes yet...
> > > > thanks again.
> > > >
> > >
> > > #{RAILS_ROOT}/lib is the appropriate place, although when it grows a
> > > little more bigger and may be reusable, its good idea to create a
> > > plugin.
> > >
> >
> >
> > Oops, replace "attribute" with x in the iterator, please.
> >
>
>
> Also, your method is a bit buggy and hence mine is too, it value
> returned by to_s will have a  "," at the end.
>
> so a better approach would be:
>
> def to_s
>   str = "#{self.class} ["
>   str << @attributes.map {|key,value| "#{key} : #{value}"}.join(',')
>   str << "]"
> end
>
>
Is inspect not a better choice?
Maybe the following code snippet proves helpfull:

430/6 > irb
irb(main):001:0> class A
irb(main):002:1> attr_accessor :a
irb(main):003:1> end
=> nil
irb(main):004:0> class B
irb(main):005:1> attr_accessor :b
irb(main):006:1> end
=> nil
irb(main):007:0> a = A.new
=> #<A:0xb7d786f8>
irb(main):008:0> b = B.new
=> #<B:0xb7d73310>
irb(main):009:0> b.b = 0x2a
=> 42
irb(main):010:0> a.a=b
=> #<B:0xb7d73310 @b=42>
irb(main):011:0> a.inspect
=> "#<A:0xb7d786f8 @a=#<B:0xb7d73310 @b=42>>"
irb(main):012:0>


HTH
Robert
-- 
You see things; and you say Why?
But I dream things that never were; and I say Why not?
-- George Bernard Shaw