Question

I have 2 models Category and Article related like this:

class Category < ActiveRecord::Base
  has_many :articles
end

class Article < ActiveRecord::Base
  belongs_to :category

  def self.count_articles_per_category
    select('category_id, COUNT(*) AS total').group(:category_id)
  end
end

I’m accessing count_articles_per_category like this

Article.count_articles_per_category

which will return articles that have 2 columns: category_id and total.

My problem is that total column is a string. So the question is: is there a method to fetch that column as an integer?

PS: I tried to do a cast in the database for COUNT(*) and that doesn’t help.
I try to avoid doing something like this:

articles = Article.count_articles_per_category
articles.map do |article|
  article.total = article.total.to_i
  article
end 

Answer 1

No, there is no support in ActiveRecord to automatically cast datatypes (which are always transferred as strings to the database).

The way ActiveRecord works when retrieving items is:

• for each attribute in the ActiveRecord model, check the column type, and cast the data to that type.
• for extra columns, it does not know what data type it should cast it to.

Extra columns includes columns from other tables, or expressions.

---

You can use a different query, like:

Article.group(:category_id).count
Article.count(:group => :category_id)

These return a hash of :category_id => count. So you might get something like {6=>2, 4=>2, 5=>1, 2=>1, 9=>1, 1=>1, 3=>1}.

Using the count method works because it implicitly lets ActiveRecord know that it is an integer type.