composing_operations.md

Composing operations

As we already have said, operations are functions taking a connection struct and returning a connection struct. As a result, a composition of operations is an operation in itself (as it also takes a connection struct and returns a connection struct).

We can leverage that to plug a whole web_pipe application as an operation to another application. By doing so, you are plugging an operation which is the composition of all operations for a given application.

class HtmlApp
  include WebPipe
  
  plug :content_type
  plug :default_status
  
  private
  
  def content_type(conn)
    conn.add_response_header('Content-Type' => 'text/html')
  end
  
  def default_status(conn)
    conn.set_status(404)
  end
end

class MyApp
  include WebPipe
  
  plug :html, HtmlApp.new
  # plug ...
end