# ri > ActionDispatch::Flash

## [ActionDispatch::Flash](https://www.chedong.com/phpMan.php/perldoc/ActionDispatch%3A%3AFlash/markdown) < Object

(from /home/chedong/.local/share/rdoc)
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The flash provides a way to pass temporary primitive-types (String,
Array, Hash) between actions. Anything you place in the flash will be
exposed to the very next action and then cleared out. This is a great
way of doing notices and alerts, such as a create action that sets
flash[:notice] = "Post successfully created" before redirecting to a
display action that can then expose the flash to its template. Actually,
that exposure is automatically done.

  class PostsController < [ActionController::Base](https://www.chedong.com/phpMan.php/perldoc/ActionController%3A%3ABase/markdown)
    def create
      # save post
      flash[:notice] = "Post successfully created"
      redirect_to @post
    end

    def show
      # doesn't need to assign the flash notice to the template, that's done automatically
    end
  end

  show.html.erb
    <% if flash[:notice] %>
      <div class="notice"><%= flash[:notice] %></div>
    <% end %>

Since the notice and alert keys are a common idiom, convenience
accessors are available:

  flash.alert = "You must be logged in"
  flash.notice = "Post successfully created"

This example places a string in the flash. And of course, you can put as
many as you like at a time too. If you want to pass non-primitive types,
you will have to handle that in your application. Example: To show
messages with links, you will have to use sanitize helper.

Just remember: They'll be gone by the time the next action has been
performed.

See docs on the FlashHash class for more details about the flash.
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## Constants:

KEY:
  [not documented]


## Class methods:

  new