Flash messages appearing twice in rails - ruby-on-rails

Question

My flash messages are appearing twice and my web research tells me this is due to render and redirect displaying the messages. I think I need to use flash.now[] or flash[] somewhere to sort this but I can't work out where it needs to go
guidelines_controller.rb
def update
#guideline = Guideline.find(params[:id])
respond_to do |format|
if #guideline.update_attributes(params[:guideline])
#guideline.update_attribute(:updated_by, current_user.id)
format.html { redirect_to #guideline, notice: 'Guideline was successfully updated.' }
format.json { head :no_content }
else
format.html { render action: "show" }
format.json { render json: #guideline.errors, status: :unprocessable_entity }
end
end
end
layouts/application.html.erb
<div class="container">
<% flash.each do |type, message| %>
<div class="alert <%= flash_class type %>">
<button class="close" data-dismiss="alert">x</button>
<%= message %>
</div>
<% end %>
</div>
application_helper.rb
def flash_class(type)
case type
when :alert
"alert-error"
when :notice
"alert-success"
else
""
end
end
guideline_controller.rb
def show
#guideline = Guideline.find(params[:id])
if #guideline.updated_by
#updated = User.find(#guideline.updated_by).profile_name
end
if User.find(#guideline.user_id)
#created = User.find(#guideline.user_id).profile_name
end
respond_to do |format|
format.html # show.html.erb
format.json { render json: #guideline }
end
end

Answer 1

You can do something like this in order to save some lines of code, and display the messages just once:
<%- if flash.any? %>
<%- flash.keys.each do |flash_key| %>
<%- next if flash_key.to_s == 'timedout' %>
<div class="alert-message <%= flash_key %>">
<a class="close" data-dismiss="alert" href="#"> x</a>
<%= flash.discard(flash_key) %>
</div>
<%- end %>
<%- end %>
By using flash.discard, you show the flash message an avoid rendering twice

Answer 2

Just putting this here for anyone else having trouble.
I had flash messages appearing twice because I had something in application.html.erb telling my app to display flash messages, but I had previously generated views with rails generate scaffold posts etc, so that had automatically added the flash messages to all the views.
So the solution was to remove them from the views.
Here's a great tutorial that demonstrates removal for just one model/view
So basically, if you have something like this in your application.html.erb:
<% if notice %>
<p class="alert alert-success"><%= notice %></p>
<% end %>
<% if alert %>
<p class="alert alert-danger"><%= alert %></p>
<% end %>
Then simply remove the equivalent from each of the views. I.e. remove this line from the top of each view
<p id="notice"><%= notice %></p>

Answer 3

I was also having the same issue and also due to another call of <%= render 'shared/alerts' %> later after my check for flash. I liked #rorra's idea of doing a flash_key. But here in the year 2020, it wasn't working as #tessad stated. It would show the message, but not format in bootstrap correctly.
I was able to change their code to work with BootStrap 4. It even dismisses as it is supposed to. The three things that needed to change were all dealing with the class of the div used to display the flash notice.
<div class="alert-message <%= flash_key %>">
alert-message becomes just alert, and the flash_key has to have alert- before it.
<div class="alert alert-<%= flash_key %>">
The last thing is I was sending it to the view from the controller as flash[:notice], which is not a recognized bootstrap alert. When I changed it to flash[:warning] it showed up correctly.
Here is the final code that worked for me. Putting it here in case anyone needs it now 7 years after the initial answer was given.
<div id="container">
<%- if flash.any? %>
<%- flash.keys.each do |flash_key| %>
<%- next if flash_key.to_s == 'timedout' %>
<div class="alert alert-<%= flash_key %>">
<a class="close" data-dismiss="alert" href="#"> x</a>
<%= flash.discard(flash_key) %>
</div>
<%- end %>
<%- end %>
</div>