The result appears in Listing 10.34

The code in Listing 10.34 has the advantage that it will break the test suite if we forget to require the user to sign in.

             The second change needed to get Listing 10.33 to work is to redefine the error messages partial so that

works. You may recall from Listing 7.22 that the error messages partial references the @user variable explicitly, but in the present case we have an @micropost variable instead. We should define an error messages partial that works regardless of the kind of object passed to it. Happily, the form variable f can access the associated object through f.object, so that in  

f.object is @user, and in

f.object is @micropost.

            To pass the object to the partial, we use a hash with value equal to the object and key equal to the desired name of the variable in the partial, which is what this code accomplishes: 

In other words, object: f.object creates a variable called object in the error_messages partial. We can use this object to construct a customized error message, as shown in Listing 10.35.