RAILS: SEARCH AND MODIFY COLUMN IN MODEL WITH PARAM PASSING FROM FORM - ruby-on-rails-4

Question

Please i have an problem: my form is that
<%=form_for :abbonamentos, url: url_for( :controller => :abbonamentos, :action => :edit) do |f| %>
<div class="field">
<%= f.label :id%><br />
<%= f.text_field :id%>
</div>
<div class="actions">
<%= f.submit %>
</div>
<% end %>
and my controller is that:
def edit
id = params[:abbonamentos][:id]
#b = Abbonamento.find_by_id(id)
#user = current_user
a=Abbonamento.find_by(user_id: #user.id)
if a and #b
a.update_column(:stato_ingresso, (a.stato_ingresso-1))
#stato = a.stato_ingresso
flash[:success] = "Abbonamento used"
redirect_to :scegli_posti
else
flash.now[:error] = "Non ha abbonamento lo deve acquistare."
end
end
I want to verify if the params id exist in the model Abbonamento...When i try i have error like this:
NoMethodError in AbbonamentosController#edit
undefined method `[]' for nil:NilClass
Thank you
Please may be I can not explain myself well. In the research I want to do I suppose the user is already registered in the Abbonamento table with his id (user_id). When the user registers in the table abbonamento, its registration that will be returned is abbonamento_id which can be 1 or 2 . When he wants to use the subscription, you will have to insert the code (abbonamento_id) there so that the application can check if the code is right or wrong before making an action. If this is true the application will make an action otherwise it will be another.
It is in fact that I would realize with rails. thank you
Started POST "/usa_abbonamento" for 127.0.0.1 at 2014-04-30 14:29:00 +0200
Processing by AbbonamentosController#edit as HTML
Parameters: {"utf8"=>"✓", "authenticity_token"=>"8Ydr6NPDkynPQd9zo42vgxNIsNSwz4SPkI0JNzfc4lQ=", "abbonamentos"=>{"id"=>"1"}, "commit"=>"Save Abbonamentos"}
[1m[35mUser Load (0.4ms)[0m SELECT "users".* FROM "users" WHERE "users"."remember_token" = 'c2bc8173fcb2c5cce4b2606962859049830be6aa' LIMIT 1
[1m[36mAbbonamento Load (0.4ms)[0m [1mSELECT "abbonamentos".* FROM "abbonamentos" WHERE "abbonamentos"."user_id" = 1[0m
[1m[35mAbbonamento Load (0.3ms)[0m SELECT "abbonamentos".* FROM "abbonamentos" WHERE "abbonamentos"."id" IS NULL
Rendered abbonamentos/edit.html.erb within layouts/application (3.2ms)
Rendered layouts/_header.html.erb (1.1ms)
Rendered layouts/_footer.html.erb (0.1ms)
Completed 200 OK in 47ms (Views: 40.2ms | ActiveRecord: 1.2ms)

Answer 1

Change your controller code as,
def edit
id = params[:abbonamentos][:id]
#b = Abbonamento.where(:id => id)
#user = current_user
a=Abbonamento.where(:user_id => #user.id)
if a.present? and #b.present?
a.update_column(:stato_ingresso, (a.stato_ingresso-1))
#stato = a.stato_ingresso
flash[:success] = "Abbonamento used"
redirect_to :scegli_posti
else
flash.now[:error] = "Non ha abbonamento lo deve acquistare."
end
end
You can make use of present? or blank? method to check if row exists.