# The symbol dilemma

**URL:** <https://www.ruby-forum.com/t/the-symbol-dilemma/146137>\
**Category:** Ruby\
**Created:** [August 18, 2008, 12:30pm UTC](https://www.ruby-forum.com/t/the-symbol-dilemma/146137 "2008-08-18T12:30:03Z")\
**Posts on this page:** 4\
**Page:** 1

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**Author:** ![Mayuresh\_K](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/m/839c29/32.png) [@Mayuresh\_K](https://www.ruby-forum.com/u/Mayuresh_K)\
**Post date:** [August 18, 2008, 12:30pm UTC](https://www.ruby-forum.com/t/the-symbol-dilemma/146137/1 "2008-08-18T12:30:03Z")

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Hi,

## There’s one more thing, I also read the following statements;

## Ruby’s hashes can use any object as a key, but Symbol objects are the most commonly used. Symbols are immutable, interned strings. They can be compared by identity rather than by textual content (because two distinct Symbol objects will never have the same content).

The statement, “because two distinct Symbol objects will never have  
the same content” seems unclear to me.

Can’t I do the following?  
books = {  
:excellent =\> “Iacocca”,  
:good =\> “Freakonomics”,  
:bad =\> “The World is Flat”,  
:ugly =\> “Guns, Germs and Steel”,  
:sick =\> “Guns, Germs and Steel”  
}

In that case, won’t two distinct Symbol objects, i.e. :ugly, and :sick  
have the same content?

I’m sure there’s something wrong in the way I’m understanding this,  
could someone please elaborate?

Thanks,

~Mayuresh

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**Author:** ![Mayuresh\_K](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/m/839c29/32.png) [@Mayuresh\_K](https://www.ruby-forum.com/u/Mayuresh_K)\
**Post date:** [August 18, 2008, 12:33pm UTC](https://www.ruby-forum.com/t/the-symbol-dilemma/146137/2 "2008-08-18T12:33:35Z")

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2008/8/18 Mayuresh K. [removed\_email\_address@domain.invalid](mailto:removed_email_address@domain.invalid):

> }
> 
> In that case, won’t two distinct Symbol objects, i.e. :ugly, and :sick  
> have the same content?
> 
> I’m sure there’s something wrong in the way I’m understanding this,  
> could someone please elaborate?

The symbols themselvs (:ugly and :sick) will always be distinct, not  
the strings they act as keys for in the hash.

Farrel

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**Author:** ![Mayuresh\_K](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/m/839c29/32.png) [@Mayuresh\_K](https://www.ruby-forum.com/u/Mayuresh_K)\
**Post date:** [August 18, 2008, 12:38pm UTC](https://www.ruby-forum.com/t/the-symbol-dilemma/146137/3 "2008-08-18T12:38:53Z")

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> > In that case, won’t two distinct Symbol objects, i.e. :ugly, and :sick  
> > have the same content?
> > 
> > I’m sure there’s something wrong in the way I’m understanding this,  
> > could someone please elaborate?
> 
> The symbols themselvs (:ugly and :sick) will always be distinct, not  
> the strings they act as keys for in the hash.

More precisely, symbols with same value are shared and point to the same  
objects in memory:

> syms = [:foo, :bar, :baz, :foo, :baz]  
> syms.map { |s| s.object\_id }  
> =\> [148818, 161538, 161618, 148818, 161618]

So, if two symbols have the same value, they are actually the very same  
object in memory. Therefore, two distinct Symbol objects must have  
different  
values.

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<div class="post-metadata">

**Author:** ![Mayuresh\_K](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/m/839c29/32.png) [@Mayuresh\_K](https://www.ruby-forum.com/u/Mayuresh_K)\
**Post date:** [August 18, 2008, 12:47pm UTC](https://www.ruby-forum.com/t/the-symbol-dilemma/146137/4 "2008-08-18T12:47:05Z")

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Mayuresh K. [removed\_email\_address@domain.invalid](mailto:removed_email_address@domain.invalid) writes:

> }
> 
> In that case, won’t two distinct Symbol objects, i.e. :ugly, and :sick  
> have the same content?

No, :ugly refers to (“has the content of”) the symbol :ugly, and :sick  
refers to the symbol :sick. The fact that you’re using different  
symbols as keys to equal values in some hash is irreleveant. What’s  
meant by the original statement is:

There are no two symbols ! :x.equal?(:y) where :x.eql?(:y)