```ruby
get '/surveys' do
  @surveys = Survey.all
  erb :"surveys/index"
end

get '/surveys/new' do
  erb :"surveys/new"
end

post '/surveys' do
  @survey = Survey.new(params[:survey])
  if @survey.save
    redirect "/surveys/#{@survey.id}"
  else
    @errors = @survey.errors.full_messages
    erb :'/surveys/new'
  end
end

get '/surveys/:id' do
  @survey = Survey.find_by(id: params[:id])
  @questions = @survey.questions
  erb :"surveys/show"
end
```

Add surveys/:id/questions index route in surveys controller
user
```ruby
get '/surveys' do
  @surveys = Survey.all
  erb :"surveys/index"
end

get '/surveys/new' do
  erb :"surveys/new"
end

post '/surveys' do
  @survey = Survey.new(params[:survey])
  if @survey.save
    redirect "/surveys/#{@survey.id}"
  else
    @errors = @survey.errors.full_messages
    erb :'/surveys/new'
  end
end

get '/surveys/:id' do
  @survey = Survey.find_by(id: params[:id])
  @questions = @survey.questions
  erb :"surveys/show"
end

get '/surveys/:survey_id/questions' do
  @survey = Survey.find_by(id: params[:survey_id])
  @questions = @survey.questions
  erb :'/questions/index'
end
```
assistant