From: David Vallner <david@...>
Date: 2006-11-13T02:18:17+09:00
Subject: Re: Help convert a Perl user to the Ruby Way.

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Sebastian Reid wrote:
> Hi all.
>=20
>     I've been working on some Ruby projects using the Rails framework
> and getting on well, however recently I've started on some projects
> using Ruby alone and have run into some issues as the task gets a littl=
e
> more complicated.
>=20
>     One particular script is giving me trouble and I suspect it is due
> to my Perly ways.  Below is a pastebin of the code.  As some I'm sure
> can tell, it is an rbot plugin that right now doesn't do a whole lot.
>=20
> http://pastebin.com/822611
>=20
>     The highlighted line is flagging up the error:
>=20
> TypeError: no implicit conversion from nil to integer
>=20
>     on line 18 (highlighted).
>=20
>     Now this is looking to me like a variable instantiation issue which=

> brings us back to Perl.  In Perl that line would be perfectly legal
> (though some would debate its elegance) and hashes and arrays would be
> created as and when required.
>=20

In Ruby, only instance variables are autovivified to nil, and that by
itself is a behaviour that gets on my nerves (typo-prone).

=46rom the code it looks @registry should be an object (maybe use a
Struct) instead of a Hash, and you should preinitialise its contents to
empty arrays and whatnot in its initialize method.

>=20
>     I'm willing to accept that this may not be the best way to do thing=
s
> in Ruby, thus I come to you to ask for a quick rundown on best practice=
s
> in these situations.
>=20
>     I've played around with default procs and the like in the
> initialisation routine to no avail. =20

Using blocks to initialize hashes / arrays is fine when not nested,
otherwise things get messy. Clean up your data structure initialisation
to be explicit?

David Vallner


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