Chapter 9. Sign In, Sign Out

Now that new users can sign up for our site (Chapter 8), it’s time to give registered users the ability to sign in and sign out. This will allow us to add customizations based on signin status and depending on the identity of the current user. For example, in this chapter we’ll update the site header with signin/signout links and a profile link; in Chapter 11, we’ll use the identity of a signed-in user to create microposts associated with that user, and in Chapter 12 we’ll allow the current user to follow other users of the application (thereby receiving a feed of their microposts).

Having users sign in will also allow us to implement a security model, restricting access to particular pages based on the identity of the signed-in user. For instance, as we’ll see in Chapter 10, only signed-in users will be able to access the page used to edit user information. The signin system will also make possible special privileges for administrative users, such as the ability (also in Chapter 10) to delete users from the database.