From: "Shot (Piotr Szotkowski)" <shot@...>
Date: 2009-11-24T04:04:33+09:00
Subject: Re: More on psuedo arrays; Better way?  Symbols v. Strings

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Ralph Shnelvar:

> MLK> Do you know the difference between symbols and strings?  A million
> MLK> strings may be generated (and quickly GC'd), but only 20 symbols wil=
l.

> I thought I did ... but apparently I didn't.

> I see that
> irb(main):001:0> "xyz01".to_sym.object_id
> =3D> 156018
> irb(main):002:0> ("xyz%02d" % 1).to_sym.object_id
> =3D> 156018

> So ....
> Do symbols hang around "forever"?  Once a symbol is
> created it is not deleted until the interpreter goes away?

It depends on the interpreter =E2=80=93 but in MRI the Symbols stay forever.

That=E2=80=99s why Rails uses Strings as keys in the params Hash=C2=B9; if =
Symbols
were used, you could theoretically create a denial of service attack by
making requests with a lot of unique GET parameters (which Rails would
turn into Symbols and MRI would not garbage-collect).

=C2=B9 Rails actually uses HashWithIndifferentAccess that
lets you access its elements using Symbol keys as well

=E2=80=94 Shot
--=20
Founding member of the Hyphenation Society, a grassroots-based,
not-for-profit, locally-owned-and-operated, cooperatively-managed,
modern-American-English-usage-improvement association.
                                                       [Rick Moen]

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