Front-End Web Development: The Big Nerd Ranch Guide

Data Down, Actions Up

Next, you will add a component to be controlled by a state change in the application. Specifically, you will create a flash alert to display a message when you create a new listing.

One of the tenets of components is “data (or state) down and actions up.” Unlike controllers, components should not change the state of an application; they should pass changes up through actions. The state of a component, on the other hand, should be passed in from a parent template – data down (Figure 25.2).

Figure 25.2  Component Data Down Actions Up

A component could easily replace a controller by passing a route’s model ...