Question

class A
  attr_accessor :dab
  ....
end

Now I have an array of instances of A, say

arr = [A.new, A.new, A.new]

And now I want to set a value to all instances of class A present in the array arr. Is there a shortcut in ruby/rails to do this?

In addition, I do have A inherited from ActiveRecord::Base

And my actual need is:

A.find_all_by_some_condition.all.dabs = 2

So, all found objects will have dab set to 2.

Is there shortcut for this?

Answer 1

To get the items of class A from an array you can use select/find_all

arr.select { |el| el.class == A } or arr.select { |el| A === el }

To achieve your actual result though you are looking to assign a value to several objects, not their corresponding class. class A does not define the actual objects it just defines the blueprint that the objects use when getting created. So finding a way to assign a value of all instances of A is not what you are after (although I might have missed the point of what you were asking for)

To assign a value to an array of object this works:

A.find_all_by_some_condition.each { |a| a.dab = 2 }

Perhaps you want to save them after that, now arr.each(&:save) might come in handy. Go look up the ampersand if you don’t know it already. Very useful.