I got four different models.
Here's an example,
@single = Single.all @coe = Coe.all @blend = Blend.all @production = @single+@coe+@blend then how to check which model @production is?
I tried
<% @production.each do |p| %> <%=p.class.name%> <% end %> but it returns "Array"
It seems to be simple, but I can't find out (I edited question)
The problem is here
@single = Single.all @coe = Coe.all @blend = Blend.all @production = @single+@coe+@blend change these lines with
@single = Single.all.to_a @coe = Coe.all.to_a @blend = Blend.all.to_a @production = @single+@coe+@blend and then if you will check
@production.first.class.name #Single @production.last.class.name #Blend so in your view you can do this
<% @production.each do |p| %> <% p.each do |product| %> <%= product.class.name %> <% end %> <% end %> 
Object.all to Object.all.to_a worked! thanks a lot!!if while iterating on @production it returns array so you need to try this.
<% @production.each do |p| %> <% p.each do |product| %> <%= product.class.name %> <% end %> <% end %> @production is a collections of combinations of single, coe, and blend thats why @production.class.name doesnt work, you need to iterate each object like this:
<% @production.each do |object| %> <%= object.class.name %> <% end %> 
@single = Single.all, @coe = Coe.all, @blend = Blend.all ? if not then results will be NilClass