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Nicely done! The app now takes in messages through a form and saves them into the database. How does this work? Let's use the request/response cycle as a guide to trace how a user's request flows through the app.

When you visit http://localhost:8000/messages/new to create a new message, it triggers the first turn of the request/response cycle:

  1. The browser makes a HTTP GET request for the URL /messages/new.
  2. The Rails router maps this URL to the Messages controller's new action. The new action creates a new Message object @message and passes it on to the view in app/views/messages/new.html.erb.
  3. In the view, form_for creates a form with the fields of the @message object.

Then when you fill out the form and press Create, it triggers the second turn of the request/response cycle:

  1. The browser sends the data to the Rails app via an HTTP POST request to the URL /messages.
  2. This time, the Rails router maps this URL to the create action.
  3. The create action uses the message_params method to safely collect data from the form and update the database.

Here we used link_to to create a link to /messages/new. Instead of hardcoding <a> elements, we can use link_to to generate links:

  • the first parameter is the link text
  • the second parameter is the URL
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