Enable Sessions

Sessions are available in Hanami applications, but not enabled by default. If we want to turn on this feature, we just need to uncomment a line of code.

# apps/web/application.rb
module Web
  class Application < Hanami::Application
    configure do
      # ...
      sessions :cookie, secret: ENV['WEB_SESSIONS_SECRET']
    end
  end
end

The first argument is the name of the adapter for the session storage. The default value is :cookie, that uses Rack::Session::Cookie.

The name of the session adapter is the underscored version of the class name under Rack::Session namespace. Example: :cookie for Rack::Session::Cookie.

We can use a different storage compatible with Rack sessions. Let’s say we want to use Redis. We should bundle redis-rack and specify the name of the adapter: :redis. Hanami is able to autoload the adapter and use it when the application is started.

Custom storage technologies are autoloaded via require "rack/session/#{ adapter_name }".

The second argument passed to sessions is a Hash of options that are passed to the adapter. We find only a default :secret, but we can specify all the values that are supported by the current adapter.

Usage

Sessions behave like a Hash: we can read, assign and remove values.

# apps/web/controllers/dashboard/index.rb
module Web
  module Controllers
    module Dashboard
      class Index
        include Web::Action
        def call(params)
          session[:b]         # read
          session[:a] = 'foo' # assign
          session[:c] = nil   # remove
        end
      end
    end
  end
end

Sharing session values between applications

To share session values, defined in one application, we must provide the same session secret to all the applications where we need those values.

# Define ENV variables for development environment
WEB_SESSIONS_SECRET="123456789"
ADMIN_SESSIONS_SECRET="123456789"

Set session variable in the first app.

# apps/web/controllers/dashboard/index.rb
module Web
  module Controllers
    module Dashboard
      class Index
        include Web::Action
        def call(params)
          session[:a] = 'foo' # assign
        end
      end
    end
  end
end

Read session variable in the second app.

# apps/admin/controllers/dashboard/index.rb
module Admin
  module Controllers
    module Dashboard
      class Index
        include Admin::Action
        def call(params)
          session[:a]         # read => 'foo'
        end
      end
    end
  end
end