class ActionDispatch::Flash - actionpack-4.2.3 Documentation

# class ActionDispatch::Flash

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
      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.

### Constants

KEY

### Public Class Methods

new(app) click to toggle source

    # File lib/action_dispatch/middleware/flash.rb, line 255
    def initialize(app)
      @app = app
    end

### Public Instance Methods

call(env) click to toggle source

    # File lib/action_dispatch/middleware/flash.rb, line 259
    def call(env)
      @app.call(env)
    ensure
      session    = Request::Session.find(env) || {}
      flash_hash = env[KEY]

      if flash_hash && (flash_hash.present? || session.key?('flash'))
        session["flash"] = flash_hash.to_session_value
        env[KEY] = flash_hash.dup
      end

      if (!session.respond_to?(:loaded?) || session.loaded?) && # (reset_session uses {}, which doesn't implement #loaded?)
        session.key?('flash') && session['flash'].nil?
        session.delete('flash')
      end
    end