From: Rolf Pedersen <rolfhsp@...>
Date: 2011-02-05T23:22:14+09:00
Subject: Re: Setter method for Hash value

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Hi Jesus

2011/2/4 Jes=FAs Gabriel y Gal=E1n <jgabrielygalan@gmail.com>

> On Fri, Feb 4, 2011 at 5:03 PM, Rolf Pedersen <rolfhsp@gmail.com> wrote:
> > Hi Jesus
> >
> > It does seem to be working. At least the example "requirements" that I
> > defined does give the expected response.
> > I have to admit, I need to study this a bit, to figure out HOW it is
> > working, though. ;o)
>
> You have two sets of requirements:
>
> 1.- Calls on the instance of MyClass: props and props=3D
> 2.- Calls on the object returned by the previous props calls: [] and []=
=3D
>
> You need to forward these 4 calls to another class. The first two are
> easy: we just implement the MyClass#props and MyClass#props=3D to do
> what we want.
>
> For the other two, you need a proxy object that can delegate [] and
> []=3D to DataClass too. For this to work, MyClass#props needs to wrap
> the actual hash returned by DataClass with a wrapper object (Props).
> As you need this proxy object to have some hash like behaviour, you
> can implement whatever methods you need to behave like a hash. As an
> example, apart from [] and []=3D I have implemented inspect and to_s.
>
>
> On Fri, Feb 4, 2011 at 3:45 PM, Brian Candler <b.candler@pobox.com> wrote=
:
>
> > Try to avoid class variables. An instance variable of the class (@data)
> > would work just as well here. @@var has really strange semantics which =
I
> > can never entirely remember, and once you've been bitten by them, you'l=
l
> > choose to use instance variables as well.
>
> I completely agree. I was in a rush when I wrote my previous post, so
> I left it as it is. Using instance variables on the DataClass object
> is cleaner:
>
> irb(main):030:0> class DataClass
> irb(main):031:1>  @data =3D {:a=3D>1, :b=3D>2, :c=3D>3}
> irb(main):032:1>  def self.get_props()
> irb(main):033:2>    @data
> irb(main):034:2>  end
> irb(main):035:1>  def self.get_prop(key)
> irb(main):036:2>    @data[key]
> irb(main):037:2>  end
> irb(main):038:1>  def self.set_props(data)
> irb(main):039:2>    @data =3D data
> irb(main):040:2>  end
> irb(main):041:1>  def self.set_prop(key, value)
> irb(main):042:2>    @data[key] =3D value
> irb(main):043:2>  end
> irb(main):044:1> end
> =3D> nil
> irb(main):045:0> c =3D MyClass.new
> =3D> #<MyClass:0xb7881b40>
> irb(main):046:0> c.props
> =3D> {:b=3D>2, :a=3D>1, :c=3D>3}
> irb(main):047:0> c.props =3D {:a =3D> 3, :b =3D> 0, :c =3D> 5, :d =3D> 6}
> =3D> {:b=3D>0, :a=3D>3, :c=3D>5, :d=3D>6}
> irb(main):048:0> c.props
> =3D> {:b=3D>0, :a=3D>3, :c=3D>5, :d=3D>6}
> irb(main):049:0> c.props[:a]
> =3D> 3
> irb(main):050:0> c.props[:a] =3D 55
> =3D> 55
> irb(main):051:0> c.props[:a]
> =3D> 55
> irb(main):052:0> c.props
> =3D> {:b=3D>0, :a=3D>55, :c=3D>5, :d=3D>6}
>
> I hope it's clearer now. Let me know if you need further help
> understanding this.
>
> Jesus.
>
>
Clear as crystal. Just what I needed! :o)
Appreciate all the help I got on this.

Best regards,
Rolf

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