It looks like you are trying to store the results of an association (has_many, habtm) in a field on a database table.
For example, if you are saving a user that has many roles, instead of having a “roles” field on your table, you would have a separate roles table and a roles_users table. The models would look like:
User - has_and_belongs_to_many :roles
Roles - has_and_belongs_to_many :users
The view would look like:
<% for role in Role.find(:all) %>
<input type=“checkbox” name=“role_ids”
value="<%= role.id %>">
<% end %>
In the controller, on the create/update you use the convenient “role_ids” method of the user object, like:
@user.role_ids = params[:role_ids]
Hope that helps.