Question

Rails 2.3.5

I have a view displaying ’employee’ records in a table where each table row haas a check_box_tag to select that (row) employee record (the table is inside a form_tag). The checkbox is passing an array of employee numbers to a method but I also need it to pass some of the other information from the record (first_name, last_name, etc) in the params.

Orignally this looked like (just passing an param with an array of employee numbers)

<% @employee_search.each do |e| %>
 <td><%= check_box_tag 'selected_subordinates[]', e.employee_number %></td>
 <td><%= e.employee_number %></td>
 <td><%= e.first_name %></td>
 <td><%= e.last_name %></td>
 ...
<% end %>

I’m not sure this was right, but I thought I should pass the entire record (‘e’) in the param:

<% @employee_search.each do |e %>
 <td><%= check_box_tag 'selected_subordinates[]', e %></td>
 <td><%= e.employee_number %></td>
 <td><%= e.first_name %></td>
 <td><%= e.last_name %></td>
 ...
<% end %>

The param array now looks like:

"selected_subordinates"=>["#<Employee:0xa946970>", "#<Employee:0xa946910>", "#<Employee:0xa9468b0>"]

I thought at this point I would be fine and just itterate through the objects in the param array referring to the record fields, but got an undefined method error:

params[:selected_subordinates].each do |s|
  puts s.last_name
end

undefined method `last_name' for "#<Employee:0xa946970>":String

I started wondering if for some reason the entire model object was passed instead of just one record from the object. But, trying [0].last_name resulted in a different error.

params[:selected_subordinates].each do |s|
  puts s.last_name
end

undefined method `last_name' for 35:Fixnum

Maybe I should have been using the fields I need to build an array for the param – so the param would be an array of arrays? I haven’t had any luck so far trying to search for example of what to do when you need to setup a param array made of arrays, or pass a single model object record (and refer to it).

Thank You – Much Appreciated!

Answer 1

When you used e as the param, Rails was converting e to a String and passing that (you can’t pass an object in an HTML form, right? Just values). When you saw "#<Employee:0xa946970>" in your params hash, it wasn’t an Employee object, but instead a String with the contents of #<Employee:0xa946970> (which is what you get if you called .to_s on an Employee object).

Passing the ID gets you on the right track, but once you have the ID, you should look up the Employee with that ID from the database.

params[:selected_subordinates].each do |s|
  employee = Employee.find(s)
  puts employee.last_name
end

Of course, this loads them one at a time, so if you have a lot of checkboxes you could end up generating a large number of queries. You can also use the find method to find multiple objects based on an array of IDs:

employees = Employee.find(params[:selected_subordinates])
employees.each do |e|
  puts e.last_name
end