Delete array element if next elements value overrides previous element value

Rails
1

Hello! For example, I have array:

[[“can”, “:manage”, “:site”, nil],
[“can”, “:view”, “:dashboard”, nil],
[“cannot”, “:manage”, “:site”, nil]]

And I want to remove [“can”, “:manage”, “:site”, nil] element, basing on
that “:manage” and “:site” elements are equal, but “cannot” element
appears later than “can”. How can i achieve that?

2

On Tue, Dec 23, 2014 at 9:50 PM, Roman Y. [email protected]
wrote:

Hello! For example, I have array:

[[“can”, “:manage”, “:site”, nil],
[“can”, “:view”, “:dashboard”, nil],
[“cannot”, “:manage”, “:site”, nil]]

And I want to remove [“can”, “:manage”, “:site”, nil] element, basing on
that “:manage” and “:site” elements are equal, but “cannot” element
appears later than “can”. How can i achieve that?

Use the middle two elements as a hash key.

-Dave

–
Dave A., consulting software developer of Codosaur.us,
PullRequestRoulette.com, Blog.Codosaur.us, and Dare2XL.com.

3

Solved it like that:

abilities_array = []
roles.map(&:abilities).flatten(1).each do |e|
if i = abilities_array.find_index{|ar| ar[1]==e[1] && ar[2]==e[2]}
abilities_array[i] = e
else
abilities_array << e
end
end
abilities_array.map{|a| “#{a[0]} #{a[1]}, #{a[2]}#{”, “+a[3] unless
a[3].blank?}”}

Maybe any suggestions how to refactor it? It looks ugly

4

On Tue, Dec 23, 2014 at 10:54 PM, Roman Y. wrote:

abilities_array.map{|a| "#{a[0]} #{a[1]}, #{a[2]}#{", "+a[3] unless

a[3].blank?}"}

I’m not even going to try to grok how that works. Using a temporary
hash as a filter is much simpler:

tmp_hash = {}
roles.map(&:abilities).each do |ability|
tmp_hash[ability[1,2]] = ability
end
abilities_array = tmp_hash.values

Or with tap:

abilities_array = {}.tap { |tmp_hash|
roles.map(&:abilities).each do |ability|
tmp_hash[ability[1,2]] = ability
end
}.values

(If you want earlier ones to take precedence, use ||= instead of =.)

Hashes are one of your bestest friends in the whole wide world. At
least, the world of Ruby. :wink: They’re very fast, and extremely
useful.

-Dave

–
Dave A., consulting software developer of Codosaur.us,
PullRequestRoulette.com, Blog.Codosaur.us, and Dare2XL.com.

5

tmp_hash = {}
roles.map(&:abilities).each do |ability|
tmp_hash[ability[1,2]] = ability
end
abilities_array = tmp_hash.values

Or with tap:

abilities_array = {}.tap { |tmp_hash|
roles.map(&:abilities).each do |ability|
tmp_hash[ability[1,2]] = ability
end
}.values

Thank you, it looks much better =)