Array and Hash how to find the value DRYest way

Rails
1

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

2

On 24 February 2011 18:29, Erwin [email protected] 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?

3

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

4

On 24 February 2011 18:29, Erwin [email protected] 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

5

On 24 February 2011 21:43, Erwin [email protected] 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! :slight_smile:

6

you’re right, rather than pushing hash into tags_on , I’ll have to
build it as a straight hash

7

On Feb 24, 1:29pm, Erwin [email protected] 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 J.

8

On 25 February 2011 17:17, Matt J. [email protected] 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