Re: Why use a symbol in place of a variable?

Along with what John Feminella said about symbols' immutability is the
advantage they have over the string literals that they also often replace,
and that is the fact that each new instance of a string literal will refer
to a different Ruby object while each reference to the equivalent symbol
will refer to the same object instance with the added bonus that less memory
is used.  See the example below.

ruby-1.9.2-p136 :001 > "hi".object_id
 => 71175750
ruby-1.9.2-p136 :002 > "hi".object_id
 => 71172980
ruby-1.9.2-p136 :003 > :hi.object_id
 => 185928
ruby-1.9.2-p136 :004 > :hi.object_id
 => 185928


On Wed, Feb 16, 2011 at 5:04 AM, sanjeev mathur <[e-mail]>wrote:

> This is quite good tutorial about symbols and strings here
>
> http://www.robertsosinski.com/2009/01/11/the-difference-between-ruby-symbols-and-strings/
>
> On Wed, Feb 16, 2011 at 6:38 AM, John Feminella <[e-mail]
> >wrote:
>
> > A symbol and a variable are two different things. A symbol is
> > essentially a special kind of literal, just like a number or a string
> > is. You cannot assign values to symbols, just like you can't assign
> > values to numbers or strings -- they are their own values. That is, it
> > makes no sense to say `42 = "banana"`, just as it makes no sense to
> > say `:banana = 42`.
> >
> > In this case, the author is using the symbol :largecave to represent a
> > particular location. The reason why he might prefer a symbol literal
> > to a string literal is that symbols are immutable. "Immutable" means
> > that you can't do operations on symbols to change them (unlike, say,
> > strings). Immutability is a good property because it decreases that
> > number of surprises you can have, and because it makes reasoning about
> > your program easier.
> >
> > ~ jf
> > --
> > John Feminella
> > Principal Consultant, BitsBuilder
> > LI: http://www.linkedin.com/in/johnxf
> > SO: http://stackoverflow.com/users/75170/
> >
> >
> >
> > On Tue, Feb 15, 2011 at 19:41, Gaba Luschi <[e-mail]>
> > wrote:
> > > Hi,
> > > Say you have a method in a class that's defined as this:
> > > (working from Peter Cooper's Beginning Ruby book, p. 155 of the book)
> > >
> > > class Dungeon
> > > .
> > > .
> > > .
> > >
> > > def start(location)
> > > @player.location = location
> > > show_current_description
> > > end
> > >
> > > why is it that when you place the player in the large cave, it's
> > > my_dungeon.start(:largecave)
> > >
> > > instead of
> > > my_dungeon.start(largecave)
> > > ?
> > > why is largecave a symbol?
> > > Thanks so much!
> > >
> > > --
> > > Posted via http://www.ruby-forum.com/.
> > >
> > >
> >
> >
>