Rails 5.0.1 Rendering to Excel not working - ruby-on-rails

Question

I have an app that helps a school to track students attendance to sports practices and games, I have all my index actions to render html, csv and xls formats and EVERYTHING GOES WELL. I have a special report that uses several model relations to complete, I am not required to render csv (I think this will be too complex to implement the to_csv method, I don't even have a clue where to put it, but this is not my problem), Now I created the equipos_controller#forma_rep method and a related view with a form to get the report's parameters, as you can see in the routes and controller code, it works fine when the report action renders the default HTML as you can see in the following log, parameters from the 'forma_rep.html.erb' form are in the params array..
Started POST "/equipos/reporte_asist" for 127.0.0.1 at 2017-01-05 18:37:51 -0600
Processing by EquiposController#reporte_asist as HTML
Parameters: {"utf8"=>"✓", "authenticity_token"=>"IP1O2bSgkGcSaUn5Sf9Tnp30yzxfP10+cA0h/1+XudoR7W8SoP6xveP3fwJpLFTvyRaBFdtqsqz5pCfYID5b5Q==", "entrenador"=>"1", "inicio"=>"2016-12-12", "final"=>"2016-12-20", "commit"=>"Crear Reporte"}
... most SQL ommited
Rendering equipos/reporte_asist.html.erb within layouts/application
Rendered equipos/reporte_asist.html.erb within layouts/application (69.4ms)
Rendered layouts/_shim.html.erb (0.5ms)
CACHE (0.0ms) SELECT "users".* FROM "users" WHERE "users"."id" = ? LIMIT ? [["id", 1], ["LIMIT", 1]]
Rendered layouts/_header.html.erb (5.9ms)
Rendered layouts/_footer.html.erb (1.1ms)
Completed 200 OK in 210ms (Views: 165.2ms | ActiveRecord: 5.6ms)
But when I click the "Excel" link :
Started POST "/equipos/reporte_asist.xls" for 127.0.0.1 at 2017-01-05 18:37:56 -0600
Processing by EquiposController#reporte_asist as XLS
Parameters: {"authenticity_token"=>"oYVjNfxN5Qxt9FHC6PpeU0wQenD3p+otaxcGts1kZRuQlUL+6 BPE1pxqZznIKVkiGPIwWXPyBb/ivgCRss2HJA=="}
User Load (0.2ms) SELECT "users".* FROM "users" WHERE "users"."id" = ? LIMIT ? [["id", 1], ["LIMIT", 1]]
Equipo Load (0.2ms) SELECT "equipos".* FROM "equipos" WHERE "equipos"."user_id" = ? [["user_id", 1]]
Completed 500 Internal Server Error in 11ms (ActiveRecord: 0.4ms)
NoMethodError (undefined method `<<' for nil:NilClass):
app/controllers/equipos_controller.rb:96:in `block in reporte_asist'
app/controllers/equipos_controller.rb:95:in `reporte_asist'
I can see that the parameters are not complete when I click the Excel link in the html file, how can I send them again? my routes work fine with the html version and the #index action renders fine in all formats, please help me.
Here is all code involved.
Routes:
resources :categorias
get '/equipos/forma_rep'
post '/equipos/reporte_asist', to: 'equipos#reporte_asist', as: 'reporte_asist'
resources :equipos
resources :players
app/controllers/equipos_controller.rb
def index
#equipos = Equipo.paginate(page: params[:page])
respond_to do |format|
format.html
format.csv { send_data #equipos.to_csv }
format.xls
end
end
# GET /equipos/forma_rep
def forma_rep
#equipo = Equipo.new
#entrenadores = User.all
end
# PUT /equipos/reporte_asist
def reporte_asist
if params[:entrenador]
#entrenador = User.find(params[:entrenador].to_i)
inicio = Time.parse(params[:inicio])
final = Time.parse(params[:final])
#equipos = #entrenador.equipos
#eventos = reporte(#entrenador.id, inicio, final)
else
#entrenador = current_user
#equipos = #entrenador.equipos
#equipos.each do |equi|
#eventos << equi.eventos
end
end
respond_to do |format|
format.html
format.xls
end
end
I have created the app/views/equipos/reporte_asist.xls.erb file with the XML directives as in..
<?xml version="1.0"?>
<Workbook xmlns="urn:schemas-microsoft-com:office:spreadsheet"
xmlns:o="urn:schemas-microsoft-com:office:office"
xmlns:x="urn:schemas-microsoft-com:office:excel"
xmlns:ss="urn:schemas-microsoft-com:office:spreadsheet"
xmlns:html="http://www.w3.org/TR/REC-html40">
<Worksheet ss:Name="Asistencias">
<Table>
<Row>
<Cell><Data ss:Type="String">Entrenador:</Data></Cell>
<Cell><Data ss:Type="String"><%= #entrenador.name %></Data> </Cell>
</Row>
....etc.
And this is the link I have in the app/views/equipos/reporte_asist.html.erb
<p>
Descargar:
<%= link_to "Excel", reporte_asist_path(format: "xls"), method: :post %>
</p>
Of course I have defined the Mime:Type.register in the config/initializers/mime_types.rb and requested the 'csv' library in my config/application.rb . I am using Rails 5.0.0.1 and Ruby 2.3.1 ...
This is the code that collects report parameter from user, it is inside the app/views/equipos/forma_rep.html.erb that posts to the reporte_asist.html.erb:
<h1>Reporte de Asistencias</h1>
<%= form_tag(reporte_asist_path) do %>
<%= label_tag(:entrenador, "Entrenador:") %>
<%= select_tag :entrenador, options_from_collection_for_select(#entrenadores, "id", "name"), prompt: "Seleccione el entrenador", class: 'form-control' %>
<%= label_tag(:inicio, "Fecha inicial de reporte:") %>
<%= date_field_tag :inicio, class: 'form-control' %>
<%= label_tag(:final, "Fecha final de reporte:") %>
<%= date_field_tag :final, class: 'form-control' %>
<%= submit_tag "Crear Reporte", class: "btn btn-default" %>
<% end %>
</div>
Initially this is the code that sends the report parameters, but once in the report view I cannot (and don't want to) re-render the form, that's why I put the link_to to the same controller but trying to render the excel

Answer 1

Add the parameters you want to POST to your reporte_asist_path helper, like this:
reporte_asist_path(format: 'xls', entrenador_id: #entrenador.id)
More information can be found here:
http://api.rubyonrails.org/classes/ActionDispatch/Routing/UrlFor.html#method-i-url_for
Also note that while using POST method for links is supported by Rails, it relies on JavaScript. If the user has JavaScript disabled, the request will fall back to GET method. So it's safer to use forms.