apply StringLiterals cop (remove double quotes, unless there is string interpolation)

app/helpers/application_helper.rb

@@ -92,17 +92,17 @@ module ApplicationHelper
 
   def getdatetime(registration, field)
     if registration.send(field.to_sym).kind_of?(String)
-      DateTime.parse(registration.send(field.to_sym)).strftime("%d %b %H:%M") if registration.send(field.to_sym)
+      DateTime.parse(registration.send(field.to_sym)).strftime('%d %b %H:%M') if registration.send(field.to_sym)
     else
-      registration.send(field.to_sym).strftime("%d %b %H:%M") if registration.send(field.to_sym)
+      registration.send(field.to_sym).strftime('%d %b %H:%M') if registration.send(field.to_sym)
     end
   end
 
   def getdate(var)
     if var.kind_of?(String)
-      DateTime.parse(var).strftime("%a, %d %b")
+      DateTime.parse(var).strftime('%a, %d %b')
     else
-      var.strftime("%a, %d %b")
+      var.strftime('%a, %d %b')
     end
   end
 
@@ -122,24 +122,24 @@ module ApplicationHelper
   end
 
   def pre_registered(event)
-    @conference.events.joins(:registrations).where("events.id = ?", event.id)
+    @conference.events.joins(:registrations).where('events.id = ?', event.id)
   end
 
   def add_association_link(association_name, form_builder, div_class, html_options = {})
-    link_to_add_association "Add " + association_name.to_s.singularize, form_builder, div_class, html_options.merge(class: "assoc btn btn-success")
+    link_to_add_association 'Add ' + association_name.to_s.singularize, form_builder, div_class, html_options.merge(class: 'assoc btn btn-success')
   end
 
   def remove_association_link(association_name, form_builder)
-    link_to_remove_association("Remove " + association_name.to_s.singularize, form_builder, class: "assoc btn btn-danger") + tag(:hr)
+    link_to_remove_association('Remove ' + association_name.to_s.singularize, form_builder, class: 'assoc btn btn-danger') + tag(:hr)
   end
 
   def dynamic_association(association_name, title, form_builder, options = {})
-    render "shared/dynamic_association", association_name: association_name, title: title, f: form_builder, hint: options[:hint]
+    render 'shared/dynamic_association', association_name: association_name, title: title, f: form_builder, hint: options[:hint]
   end
 
   # Same as redirect_to(:back) if there is a valid HTTP referer, otherwise redirect_to()
   def redirect_back_or_to(options = {}, response_status = {})
-    if request.env["HTTP_REFERER"]
+    if request.env['HTTP_REFERER']
       redirect_to(:back)
     else
       redirect_to(options, response_status)
@@ -148,7 +148,7 @@ module ApplicationHelper
 
   # TODO Output better html
   def format_comments(comment, padding = 0)
-    result = ""
+    result = ''
     result += "<div style='padding-left:#{padding}px'>"
     result += "<div class='well'>"
     result += "<b>#{comment.user.name}</b> <i>#{comment.created_at}</i><br><br>"
@@ -160,12 +160,12 @@ module ApplicationHelper
     result += "<input name='authenticity_token' type='hidden' value='#{form_authenticity_token}' />"
     result += "<textarea name='comment'></textarea>"
     result += "<button class='btn btn-primary pull-right' name='button' type='submit'>Add Reply</button>"
-    result += "</form></div></div>"
-    result += "</div>"
+    result += '</form></div></div>'
+    result += '</div>'
     #result += edit_admin_conference_event_path(@conference.short_title, @event)
     comment.children.each do |child|
       result += format_comments(child, 50)
-      result += "</div>"
+      result += '</div>'
     end
 
     result
@@ -181,7 +181,7 @@ module ApplicationHelper
     markdown.render(text).html_safe
   end
 
-  def markdown_hint(text="")
+  def markdown_hint(text='')
     markdown("#{text} Please look at #{link_to '**Markdown Syntax**', 'https://daringfireball.net/projects/markdown/syntax', target: '_blank'} to format your text")
   end