Counting occurences in an array and sorting in Ruby on Rails

Question

I have an array returned by the function Search.all :

=> [#<Search id: 7, name: "ap", presence: true, created_at: "2012-03-16 00:58:42", updated_at: "2012-03-16 00:58:42">, #<Search id: 8, name: "papier", presence: true, created_at: "2012-03-16 01:14:32", updated_at: "2012-03-16 01:14:32">, #<Search id: 9, name: "carton de jus", presence: true, created_at: "2012-03-20 22:28:53", updated_at: "2012-03-20 22:28:53">, #<Search id: 10, name: "carton de jus", presence: true, created_at: "2012-03-20 22:29:01", updated_at: "2012-03-20 22:29:01">, #<Search id: 11, name: "Papier", presence: true, created_at: "2012-03-22 20:43:36", updated_at: "2012-03-22 20:43:36">, #<Search id: 12, name: "Papier", presence: true, created_at: "2012-03-22 20:43:47", updated_at: "2012-03-22 20:43:47">, #<Search id: 13, name: "Salut", presence: false, created_at: "2012-03-24 20:34:49", updated_at: "2012-03-24 20:34:49">, #<Search id: 14, name: "carton", presence: true, created_at: "2012-03-26 19:32:03", updated_at: "2012-03-26 19:32:03">, #<Search id: 15, name: "carton", presence: true, created_at: "2012-03-26 19:32:11", updated_at: "2012-03-26 19:32:11">, #<Search id: 16, name: "carton", presence: true, created_at: "2012-03-26 19:32:15", updated_at: "2012-03-26 19:32:15">, #<Search id: 17, name: "cellulaire", presence: true, created_at: "2012-03-26 19:32:28", updated_at: "2012-03-26 19:32:28">, #<Search id: 18, name: "cellulaire", presence: true, created_at: "2012-03-26 19:32:36", updated_at: "2012-03-26 19:32:36">, #<Search id: 19, name: "montre", presence: false, created_at: "2012-03-29 00:45:26", updated_at: "2012-03-29 00:45:26">, #<Search id: 20, name: "montre", presence: false, created_at: "2012-03-29 00:45:29", updated_at: "2012-03-29 00:45:29">, #<Search id: 21, name: "montres", presence: false, created_at: "2012-03-29 00:45:32", updated_at: "2012-03-29 00:45:32">, #<Search id: 22, name: "montre", presence: false, created_at: "2012-03-29 00:45:35", updated_at: "2012-03-29 00:45:35">]

I want to count the number of occurences of the same elements based on "name". I know how to find the occurences in an array like this one : ['a', 'b', 'a'] with

favoris.inject(Hash.new(0)) { |h,v| h[v] += 1; h }

But how can use that in the previous array?

Simple. Replace h[v] with h[v.name] (or however you get the name). — Linuxios
– Linuxios, Commented Mar 29, 2012 at 0:56

Nick Kezhaya · Accepted Answer · 2012-03-29 00:58:44Z

6

favoris.inject(Hash.new(0)) { |h,v| h[v.name] += 1; h }

:)

answered Mar 29, 2012 at 0:58

Nick Kezhaya

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1 Comment

Justin D. Over a year ago

I needed to wait 8 minutes before I could.

asymmetric · Accepted Answer · 2013-11-09 12:51:53Z

0

I prefer a solution based on each, as you're actually iterating on every element of the array, while producing side effects. That, for how I understand it, is not the reason inject was created.

h = Hash.new(0)
favoris.each { |el| h[el] += 1 }

answered Nov 9, 2013 at 12:51

asymmetric

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