The Flash

Before submitting a valid registration in a browser, we’re going to add a bit of polish common in web applications: a message that appears on the subsequent page (in this case, welcoming our new user to the application) and then disappears upon visiting a second page or on pagereload. The Rails way to accomplish this is to use a special variable called the flash, which operates like flash memory in that it stores its data temporarily. The flash variable is effectively a hash; you may even recall the console example in Section 4.3.3, where we saw how to iterate through a hash using a strategically named flash hash:

We can arrange to display the contents of the flash site-wide by including it in our application layout, as in Listing 7.26. (This code is a particularly ugly combination of HTML and ERb; an exercise in Section 7.6 shows how to make it prettier.)