Scaffold Our Shopping Cart (Part II)

Sync all tabs

One important aspect of our application design is that all the user’s tabs stay in sync. Because each tab is a different Channel instance, we need to link the Channels to each other. The simplest way to do this is via the Channel topic. Two Channels with the topic cart:123 should be linked together. They should be separate from a Channel with the topic cart:345.

Browser cookies are a great place to store semi-permanent data. We will generate and store a random identifier in the cookie session so that multiple tabs share the same identifier. First, we need a way to generate a random cart ID. It is best to use :crypto.strong_rand_bytes/1 for this purpose. Add the following function to the Checkout module: