Re: Learning and stuck `OpenStruct` standard library of Ruby

On 2013-05-24, at 6:44 AM, Love U Ruby <[e-mail]> wrote:

> Hi,
>=20
> I was learning Ruby's standard library `OpenStruct`. And doing so,out =
of
> curiosity wrote the below code:
>=20
> require 'ostruct'
>=20
> person =3D OpenStruct.new
> person.name    =3D "John Smith"
> person.age     =3D 70
> person.pension =3D 300
>=20
> p person.instance_variables #=3D> [:@table, :@modifiable]
>=20
> Now my question is - Where the above 2 instance variables have been
> defined? What are their uses.
>=20
> On the same not I also not able to understand the method =
`#modifiable`.
> =
(http://www.ruby-doc.org/stdlib-2.0/libdoc/ostruct/rdoc/OpenStruct.html#me=
thod-i-modifiable).
>=20
> Can any one help me to understand the same?

You might be able to help yourself by using a tool like pry =
http://pryrepl.org to look at the variables and source.  For example

ratdog:~ mike$ pry
[1] pry(main)> require 'ostruct'
=3D> false
[2] pry(main)>
[3] pry(main)> person =3D OpenStruct.new
=3D> #<OpenStruct>
[4] pry(main)> person.name    =3D "John Smith"
=3D> "John Smith"
[5] pry(main)> person.age     =3D 70
=3D> 70
[6] pry(main)> person.pension =3D 300
=3D> 300
[7] pry(main)> person
=3D> #<OpenStruct name=3D"John Smith", age=3D70, pension=3D300>
[8] pry(main)> cd person
[9] pry(#<OpenStruct>):1> $ to_s

From: /Users/mike/.rbenv/versions/2.0.0-p0/lib/ruby/2.0.0/ostruct.rb @ =
line 232:
Owner: OpenStruct
Visibility: public
Number of lines: 21

def inspect
  str =3D "#<#{self.class}"

  ids =3D (Thread.current[InspectKey] ||=3D [])
  if ids.include?(object_id)
    return str << ' ...>'
  end

  ids << object_id
  begin
    first =3D true
    for k,v in @table
      str << "," unless first
      first =3D false
      str << " #{k}=3D#{v.inspect}"
    end
    return str << '>'
  ensure
    ids.pop
  end
end

I have found pry and its add-ons to be very useful for exploring bits of =
ruby code.

Mike

--=20

Mike Stok <[e-mail]>
http://www.stok.ca/~mike/

The "`Stok' disclaimers" apply.