From: Bill Atkins <batkins57@...>
Date: 2005-04-21T00:18:12+09:00
Subject: Re: [NEWBIE]: Example from Pickaxe2 gives errors... (p. 31)

------=_Part_6379_14909240.1114010266294
Content-Type: text/plain; charset=ISO-8859-1
Content-Transfer-Encoding: quoted-printable
Content-Disposition: inline

Song doesn't have a constructor defined in that example. When you call=20
Blah.new, Ruby creates a new instance of Blah and then calls the method=20
initialize on that instance.

If you had:

class Song
attr_writer :name, :artist, :duration
def initialize name, artist, duration
@name, @artist, @duration =3D name, artist, duration
end
end

then calling Song.new("Title", "Artist", 56) would give you an object with=
=20
the appropriate values set. When you call Song.new(param1, param2, param3),=
=20
Ruby tries to pass those three parameters to the initialize method in Song.=
=20
But since initialize doesn't exist, it calls the default initialize, which=
=20
takes no parameters - that explains the error you got.

Hope that helps.


On 4/20/05, Simon.Mullis@equinoxsolutions.com <
Simon.Mullis@equinoxsolutions.com> wrote:
>=20
> Greeting all,
>=20
> How about a refreshingly easy question for a change....
>=20
> Really, really basic question I know, but:
>=20
> class Song
> attr_writer :name, :artist, :duration
> end
> =3D> nil
>=20
> song =3D Song.new("Blueberry Hill", "Fats Waller", 320)
> =3D> ArgumentError: wrong number of arguments (3 for 0)
> from (irb):24:in `initialize'
> from (irb):24:in `new'
> from (irb):24
>=20
> However....
>=20
> song =3D Song.new()
> =3D> #<Song:0x2aab648>
>=20
> song.name <http://song.name> =3D "Blueberry Hill"
> =3D> "Blueberry Hill"
>=20
> song.name <http://song.name>
> =3D> "Blueberry Hill"
>=20
> Have I misread / misunderstood the text? Why the errors?
>=20
> SM
>=20
> (Only 770 pages to go... Woohoo!)
>=20
>=20
> -------------------------------------------------------------------------=
-----------------
> Equinox Converged Solutions
> Tel: +44 (0)1252 405 600
> http://www.equinoxsolutions.com
> Equinox Converged Solutions is a trading name of Synetrix Holdings=20
> Limited.
>=20
> IMPORTANT NOTICE:
> This message is intended solely for the use of the Individual or=20
> organisation to whom it is addressed. It may contain privileged or=20
> confidential information. If you have received this message in error, ple=
ase=20
> notify the originator immediately.
> If you are not the intended recipient, you should not use, copy, alter, o=
r=20
> disclose the contents of this message. All information or opinions expres=
sed=20
> in this message and/or any attachments are those of the author and are no=
t=20
> necessarily those of Synetrix Holdings Limited.
> Synetrix Holdings Limited accepts no responsibility for loss or damage=20
> arising from its use, including damage from virus.
>=20
> -------------------------------------------------------------------------=
------------------
>=20
>=20


--=20
Bill Atkins

------=_Part_6379_14909240.1114010266294--