The Elm Architecture

Gren applications follow The Elm Architecture.

There are three main concepts with this type of architecture:

• Model: Holds your application state. “Application state” is the runtime data your application cares about. For example, the current logged in user might be part of your model.
• View: Renders the UI for your application state. This might be an HTML page, a JSON response, or some text on the command line.
• Update: Modifies your application state in response to events. Maybe a user clicked logout, so you return a new model with the user removed.

As your application runs, the path through the architecture looks like this:

In the next sections we’ll cover how to write programs that use this architecture.