Rails - Feb 2011 - Array and Hash ... how to find the value ? DRYest way

I have an array of hash :
tags_on
 => [{:point=>["a", "b", "c"]},
{:comma=>["d", "e"]}]

and I would like to get the value ["d", "e"] for a specified
key  :comma
is there any DRY way to do it or should I loop into the array ?

thanks for your feedback

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On 24 February 2011 18:29, Erwin
<yves_dufour-ee4meeAH724@public.gmane.org> wrote:
> I have an array of hash :
> tags_on
>  => [{:point=>["a", "b", "c"]},
{:comma=>["d", "e"]}]

What if your array of hashes looks like this:

  [{:point=>["a", "b", "c"],
:comma=>["f", "g"]}, {:comma=>["d",
"e"]}]

..how would you know which :comma key to retrieve?

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On 24 February 2011 18:29, Erwin
<yves_dufour-ee4meeAH724@public.gmane.org> wrote:
> I have an array of hash :
> tags_on
>  => [{:point=>["a", "b", "c"]},
{:comma=>["d", "e"]}]
>
> and I would like to get the value ["d", "e"] for a
specified
> key  :comma
> is there any DRY way to do it or should I loop into the array ?
Assuming the keys are unique why don''t you build it as a straight hash
in the first place?  If they are not unique then you are in trouble
anyway.  If you are stuck with the array then I think I would use
collect to convert it into a straight hash first.

Colin

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they wil be unique , before adding a new hash, I''ll have to check if
the key already exist
but I agree with Colin, better build a straight hash first

On 24 fév, 20:06, Michael Pavling
<pavl...-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>
wrote:
> On 24 February 2011 18:29, Erwin
<yves_duf...-ee4meeAH724@public.gmane.org> wrote:
>
> > I have an array of hash :
> > tags_on
> >  => [{:point=>["a", "b", "c"]},
{:comma=>["d", "e"]}]
>
> What if your array of hashes looks like this:
>
>   [{:point=>["a", "b", "c"],
:comma=>["f", "g"]}, {:comma=>["d",
"e"]}]
>
> ..how would you know which :comma key to retrieve?
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you''re right, rather than pushing hash into tags_on , I''ll
have to
build it as a straight hash

On 24 fév, 22:09, Colin Law
<clan...-gM/Ye1E23mwN+BqQ9rBEUg@public.gmane.org>
wrote:
> On 24 February 2011 18:29, Erwin
<yves_duf...-ee4meeAH724@public.gmane.org> wrote:
>
> > I have an array of hash :
> > tags_on
> >  => [{:point=>["a", "b", "c"]},
{:comma=>["d", "e"]}]
>
> > and I would like to get the value ["d", "e"] for a
specified
> > key  :comma
> > is there any DRY way to do it or should I loop into the array ?
>
> Assuming the keys are unique why don''t you build it as a straight
hash
> in the first place?  If they are not unique then you are in trouble
> anyway.  If you are stuck with the array then I think I would use
> collect to convert it into a straight hash first.
>
> Colin
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On 24 February 2011 21:43, Erwin
<yves_dufour-ee4meeAH724@public.gmane.org> wrote:
> they wil be unique , before adding a new hash, I''ll have to check
if
> the key already exist
> but I agree with Colin, better build a straight hash first
That''s kindof what I was getting at - if the keys are unique, you
don''t have an array of hashes, you have a hash! :-)

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On Feb 24, 1:29 pm, Erwin <yves_duf...-ee4meeAH724@public.gmane.org>
wrote:
> I have an array of hash :
> tags_on
>  => [{:point=>["a", "b", "c"]},
{:comma=>["d", "e"]}]
>
> and I would like to get the value ["d", "e"] for a
specified
> key  :comma
> is there any DRY way to do it or should I loop into the array ?
For reference, this will do what you''re looking for (array starts in
tags_on, key in desired_key):

hash = tags_on.detect { |h| h.has_key?(desired_key) }
result = hash[desired_key] if hash

I''ve had to build little arrays of single-key hashes like this to work
around 1.8.6 not having ordered hash semantics.

--Matt Jones

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On 25 February 2011 17:17, Matt Jones
<al2o3cr-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>
wrote:
> I''ve had to build little arrays of single-key hashes like this to
work
> around 1.8.6 not having ordered hash semantics.
...or you have a normal hash with one of the values as an array of the
keys in the order you want (I normally call it ":order"). Then when
you want to iterate you hash in order:

my_hash = {:name => "fred", :order => [:age, :foo, :name], :age
=>
"21", :foo => "bar"}
my_hash[:order].each do |key|
  puts my_hash[key]
end

Keeps it all "standard" and in one object... YMMV

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