Question

Relating to my last question here: Rails: Finding all associated objects to a parent object

Is it possible to sort multiple separate child objects in Rails by creation date, and then list them? Using the previous example I have a resume with two different has_many child objects, I would like to fetch them and then sort them based on creation date and then use that to display them.

Answer 1

I assume that you have two (or more) seperate models for children objects, so your Parent model looks like this:

class Parent < ActiveRecord::Base
  has_many :dogs
  has_many :cats
end

To sort them and get them generally as children you can write method (similar to @gertas answer):

def children
  @children ||= (self.dogs.all + self.cats.all).sort(&:created_at)
end

and put it in Parent model. Then you can use it in controller:

@parent = Parent.find(params[:id])
@children = @parent.children

Now we’ll try to display them in a view. I assume that you have created two partials for each model _cat.html.erb and _dog.html.erb. In view:

<h1>Children list:</h1>
<% @parent.children.each do |child| %>
  <%= render child %>
<% end %>

It should automaticaly find which partial should be used, but it can be used only if you follow Rails way. If you want to name partials in different way, or store it in different directory, then you would have to write your own methods that will choose correct partial based on type od object.