In Rails, is it possible to display an alert without calling redirect_to or render?

Answer 1

You should use remote: true in your form.

<%= form_tag generate_report_path(:header => true), remote: true do |f| % >
<div class="container-fluid">
  <div style="padding-right:10px">
   <%= select_tag(:report_id, options_for_select(
      [["Select Report Type", 0],
      ["Report1", 1],
      ["Report2", 2],
      ["Report3", 3]]), id: "report_selection") 
   %>
   <%= hidden_field_tag :format, :pdf %>
   <%= button_tag "Generate Report", class: 'btn btn-sm btn-primary'%>
   <%= label_tag do %>
     <%= check_box_tag "format_reqd", "format_reqd", false %>
     Check for Numeric format 
   <% end %>

<% end  %>

Above remote: true is responsible for sending ajax request to your controller method. Here is a complete guide for form_for and remote requests.

In your method of the controller:

def generate_report
  ... #Whatever you want to add here.
  render js: "alert('Your report would be emailed to you in a few minutes')"
end

Update with the flash message:

Your controller method will now look like:

def generate_report
  ... #Whatever you want to add here.
  respond_to do |format|
    format.js { flash[:notice] = "Your report would be emailed to you in a few minutes" }
  end
end

Rendered view:

# app/views/users/generate_report.js.erb
$("#flash").html('<%= j render partial: "shared/notice_banner" %>');

# app/views/layouts/application.html.erb
<div id="flash">
  <% if notice.present? %>
    <%= render partial: "shared/notice_banner" %>
  <% end %>
</div>


# app/views/shared/_notice_banner.html.erb
<div data-alert class="alert-box">
  <%= notice %>
  <a href="#" class="close">&times;</a>
</div>

Here is the detailed answer present. Hope this will help.