Question

I am using Ruby on Rails 3.0.7 and I would like to keep the ActiveRecord::Relation class after doing this (in the below code article_category_relationships represents an has_many :through Record Association):

# @article.article_category_relationships.class               # => ActiveRecord::Relation
@article.article_category_relationships.map(&:category).class # => Array

It should be something like this:

@article.article_category_relationships.map(&:category).class # => ActiveRecord::Relation

It seems that the map method makes losing the ActiveRecord::Relation class.

Is it possible to keep the ActiveRecord::Relation class after run an iterative method? If so how can do?

Note: I would like that in order to keep using of all methods provided by Ruby on Rails for the ActiveRecord::Relation class (.where(...), .count, …).

Answer 1

If you are using ruby 1.9, check out tap:

obj.tap{|x|...} => obj
Yields x to the block, and then returns x. The primary purpose of this method is to "tap into" a method chain, in order to perform operations on intermediate results within the chain.

    (1..10)                .tap {|x| puts "original: #{x.inspect}"}
      .to_a                .tap {|x| puts "array: #{x.inspect}"}
      .select {|x| x%2==0} .tap {|x| puts "evens: #{x.inspect}"}
      .map { |x| x*x }     .tap {|x| puts "squares: #{x.inspect}"}