Conditional value in helper method in ruby

Question

I would like to set a parameter in this helper method, but I'm not sure if is possible to use a ternary operator or something to set a value with some condition.

<%= number_field_tag 'somearray[][somefield]', nil, {min: 0.000, step: 0.001, class: "form-control", :'aria-label' => "Quantity" ,onchange: "change_total(this)",value: 'VALUE SHOULD BE HERE'} %>

The condition is something like this:

if params['somearray'].nil? != true
   return params['somearray'].first["quantity"]
else
   return nil
end

Answer 1

The second argument of number_field_tag is actually the value, so you can certainly set it there with a ternary operator (which I've simplified based on the fact that nil is falsy):

number_field_tag 'somearray[][somefield]', (params[:somearray] ? params[:somearray][0][:quantity] : nil), min: 0.000, step: 0.001, class: "form-control", :'aria-label' => "Quantity", onchange: "change_total(this)"

However, complex in-line view operations are best refactored to a helper file. Helper files are defined in the app/helpers directory and named based on the controller: if you have a PagesController , you'd want to add the method to module PagesHelper in app/helpers/pages_helper.rb (note that the params method is still accessible from the helper file even without passing it in):

def somearray_value
  params[:somearray] ? params[:somearray][0][:quantity] : nil
end

Then you can call it in the view:

number_field_tag 'somearray[][somefield]', somearray_value, min: 0.000, step: 0.001, class: "form-control", :'aria-label' => "Quantity", onchange: "change_total(this)"

Answer 2

您可以使用try ：

<%= number_field_tag 'somearray[][somefield]', params[:somearray].try(:first).try(:fetch, :quantity), {min: 0.000, step: 0.001, class: "form-control", :'aria-label' => "Quantity" ,onchange: "change_total(this)" %>