/ Ruby on Rails
/
method

to_formatted_s

v5.1.7 - Show latest stable - Class: Array
to_formatted_s(format = :default)
public

Extends Array#to_s to convert a collection of elements into a comma separated id list if :db argument is given as the format.

Blog.all.to_formatted_s(:db)  # => "1,2,3"
Blog.none.to_formatted_s(:db) # => "null"
[1,2].to_formatted_s          # => "[1, 2]"

2Notes

Don't Use to_formatted_s(:db) on an Array of IDs

joshuapinter · May 26, 2011

I thought using to_formatted_s(:db) on an array of ids would separate them with commas in a nice way. Wrong. It does, but it also changes the numbers. === Wrong [60, 271, 280, 283].to_formatted_s(:db) # => "121,543,561,567" # Completely different numbers!

Instead, use the join method: === Right [60, 271, 280, 283].join(",") # => "60,271,280,283" # Much better

I think this has to do with (:db) being used for formatting dates but I'm not sure.

RE: Don't Use to_formatted_s(:db) on an Array of IDs

etmoyo · Jun 23, 2011

The reason it doesnt work @joshuapinter for IDs is because if you look at the source:

case format
  when :db
    if respond_to?(:empty?) && self.empty?
      "null"
    else
      collect { |element| element.id }.join(",") # look at this line
    end
  else
    to_default_s
end

It maps/collects the object ids and then joins them using a comma ; so in the case of 60 for instance :

60.object_id #=> 121

60.id #=> 121