:"#{name}="
···
On Jun 20, 2012, at 15:25 , Hal Fulton wrote:
(name.to_s << "=").to_sym
So then, in what cases would it be helpful to use them interchangeably?
Is it possible to define a common, useful interface that both Symbol
and String could implement. If so, perhaps a class or module could be
defined for that interface and incorporated into both classes as
appropriate.From what I've seen, the most frequently voiced desire is to be able to
use apparently equivalent symbols and strings as fully equivalent hash
keys.Even that would not be solved by inheritance because instance of
different classes can never be equivalent.
I didn't mean to imply that it would. Personally, I prefer having Hash
be picky about these things. That generality allows it to be used as
the basis for something like HashWithIndifferentAccess without much
fuss. Doing things the other way around would be much more difficult.
To be honest, the best way to handle this particular issue would
probably be to add some syntactic sugar that makes it as easy to
instantiate HashWithIndifferentAccess as it is to instantiate Hash.
Assuming HashWithIndifferentAccess is available, maybe something like this:
def h(regular_hash)
HashWithIndifferentAccess.new(regular_hash)
end
hash = h :a => 1, 'b' => 2
puts hash['a'] #=> 1
puts hash[:b] #=> 2
PS: I said "If at all..." - so I am not a fan of String as subclass of
Symbol either.
To me, Symbol and String really are very different things. Symbol
effectively *has* a frozen String instance associated with it but is not
itself the String instance. The String#to_sym method is just a
convenience method to perform a reverse lookup on such associations,
creating them if they don't already exist.
In other words, there is an implicit hash that maps Symbol instances to
String instances (a... ahem... symbol table). Saying that Symbol and
String should have some sort of direct ancestral class relationship with
one another based on that fact alone is like saying that the keys and
values in your own hashes should always have such a relationship as
well. Clearly, or perhaps not so clearly, that's nonsense. 
-Jeremy
···
On 06/20/2012 05:43 PM, Robert Klemme wrote:
On Thu, Jun 21, 2012 at 12:25 AM, Hal Fulton <rubyhacker@gmail.com> wrote:
On Wed, Jun 20, 2012 at 5:06 PM, Jeremy Bopp <jeremy@bopp.net> wrote:
Ryan Davis wrote in post #1065463:
···
On Jun 20, 2012, at 15:25 , Hal Fulton wrote:
(name.to_s << "=").to_sym
:"#{name}="
By the way :
In Sequel, you have to write something like '.order(:name.desc)' to ask
for a reverse ordering of a field. How, given the symbol :name, do you
build the symbol :name.desc, without some sort of 'eval' ?
_md
--
Posted via http://www.ruby-forum.com/\.
As I understand it, interpolation is not eval, so you answered your own question (or at least included it).
:"#{name}.desc"
ymmv since my iPhone doesn't run ruby 
···
On Jun 25, 2012, at 8:14 AM, Michel Demazure <lists@ruby-forum.com> wrote:
Ryan Davis wrote in post #1065463:
On Jun 20, 2012, at 15:25 , Hal Fulton wrote:
(name.to_s << "=").to_sym
:"#{name}="
By the way :
In Sequel, you have to write something like '.order(:name.desc)' to ask
for a reverse ordering of a field. How, given the symbol :name, do you
build the symbol :name.desc, without some sort of 'eval' ?_md
--
Posted via http://www.ruby-forum.com/\.
I think Sequel defines the method #desc on Symbol to make this work.
-- Matma Rex
···
2012/6/25 Michel Demazure <lists@ruby-forum.com>:
By the way :
In Sequel, you have to write something like '.order(:name.desc)' to ask
for a reverse ordering of a field. How, given the symbol :name, do you
build the symbol :name.desc, without some sort of 'eval' ?
You've already gotten a good answer (Symbol#desc) but I wanted to add some clarification on how your example above is seen by ruby:
3431 % pwd
/Users/ryan/Work/p4/zss/src/ruby_parser/dev/
3432 % rake debug R="a.order(:name.desc)"
s(:call, s(:call, nil, :a), :order, s(:call, s(:lit, :name), :desc))
···
On Jun 25, 2012, at 08:14 , Michel Demazure wrote:
In Sequel, you have to write something like '.order(:name.desc)' to ask
for a reverse ordering of a field. How, given the symbol :name, do you
build the symbol :name.desc, without some sort of 'eval' ?
-------------------------------
Alex Chaffee wrote in post #1065959:
As I understand it, interpolation is not eval, so you answered your own
question (or at least included it).:"#{name}.desc"
ymmv since my iPhone doesn't run ruby
True ! Sorry !!
_md
···
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Posted via http://www.ruby-forum.com/\.
Ryan Davis wrote in post #1066026:
···
On Jun 25, 2012, at 08:14 , Michel Demazure wrote:
In Sequel, you have to write something like '.order(:name.desc)' to ask
for a reverse ordering of a field. How, given the symbol :name, do you
build the symbol :name.desc, without some sort of 'eval' ?You've already gotten a good answer (Symbol#desc) but I wanted to add
some clarification on how your example above is seen by ruby:3431 % pwd
/Users/ryan/Work/p4/zss/src/ruby_parser/dev/
3432 % rake debug R="a.order(:name.desc)"
s(:call, s(:call, nil, :a), :order, s(:call, s(:lit, :name), :desc))
-------------------------------
Thanks, Ryan and Bartosz, for your help !
_md
--
Posted via http://www.ruby-forum.com/\.
Michel Demazure wrote in post #1065964:
Alex Chaffee wrote in post #1065959:
As I understand it, interpolation is not eval, so you answered your own
question (or at least included it).:"#{name}.desc"
ymmv since my iPhone doesn't run ruby
True ! Sorry !!
_md
Checked again. This does not work with a dot in the string :
:"name" => :name
:"name.desc" => :"name.desc"
_md
···
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