how to pass all student_id in checkbox - ruby-on-rails

Question

I am having check box for selecting students in a particular class.But the unselected student id's are not passing via check box.Please help me. And also I have included coding below.
In View
<%= label_tag :students %>
<button type="button" id="check_all">
Check / Uncheck All
</button>
<table id = "mark">
<tr>
<td>
<table >
<thead>
<tr>
<td><strong>Students List</strong></td>
</tr>
</thead>
<tbody>
<% #student.each do |i| %>
<tr>
<td><%= check_box_tag :student, i.id %><%= i.first_name.capitalize %></td>
</tr>
<% end %>
</tbody>
</table>
<table>
<tr>
<td>
</tr>
</td>
</table>
</td>
</tr>
</table>
Js file
$('#check_all').on("click", function(){ $('input[type="checkbox"]').click(); });

Answer 1

You can achieve that in two ways at least.
one) deducting the submitted students from the students collection ids:
unselected_ids = #student.collect(&:id) - params[:student].collect(&:to_i)
two) setting another hidden field from client site using javascript

Answer 2

You can use hidden input with the same name before checkbox and zero value.
<input type='hidden' value='0' name='student'>
<input type='checkbox' value='1' name='student'>
When form submitted and checkbox is checked previous 0 value overwrites by 1. If checkbox not checked then 0 value sends to the controller.
Bur its works only if you have one value, but you have a lot of ids. And you must use student[] name in checkboxes, if you use student name then only last checked value sends in controller by in params[:student]
In this case use can use this construction in your code:
<% #student.each do |s| %>
<tr><td>
<%= hidden_field_tag "student_all[]", s.id %>
<%= check_box_tag "student[]", s.id %><%= s.first_name.capitalize %>
</td></tr>
<% end %>
And in controller get unchecked students like:
student_unchecked = params[:student_all] - params[:student]