We can visualize the result of this association in Figure 2.15. Because of the user_id column in the microposts table, Rails (using Active Record) can infer the microposts associated with each user.

In Chapter 10 and Chapter 11, we will use the association of users and microposts both to display all a user’s microposts and to construct a Twitter-like micropost feed. For now, we can examine the implications of the user-micropost association by using

the console, which is a useful tool for interacting with Rails applications. We first invoke the console with rails console at the command line, and then retrieve the first user from the database using User.first (putting the results in the variable first_user):7

(I include the last line just to demonstrate how to exit the console, and on most systems you can Ctrl-d for the same purpose.) Here we have accessed the user’s microposts using the code first_user.microposts: With this code, Active Record automatically returns all the microposts with user_id equal to the id of first_user (in this case, 1). We’ll learn much more about the association facilities in Active Record in Chapter 10 and Chapter 11.