Rosmaro

Reacting to the same action in different ways due to what happened in the past may be a challenge.

Rosmaro is a framework for writing functions like this:

({state, action}) => ({state, result})

Check out the Rosmaro documentation at rosmaro.js.org!

Get Rosmaro using npm: npm i rosmaro.

Rosmaro places great emphasis on two programming paradigms:

• Visual programming - changes of behavior are drawn using the Rosmaro visual editor.
• Functional programming - the whole model is a pure function built out of pure functions and pure data.

First, you draw a graph. Then, you assign functional code to its nodes.

It gives you:

• Automata-based dispatch - actions are dispatched to handlers based on the current node of the state machine. There's no need to check the current state.
• The right model for the job - the behavior-related state is expressed by a state machine, while the data-related state lives in a dictionary.
• Existing tooling - it's easy to use with redux and redux-saga.

Rosmaro models support:

• Node multiplication - a node may be multiplied using a function of the context.
• Reuse and composition - models may be included within other models.
• Lenses - thanks to Ramda lenses the shape and size of your data-related state may be easily adjusted.
• Orthogonal regions - multiple regions may be active at the same time. One of the ways to avoid state explosion.
• Subgraphs - nodes of state machines may contain other state machines.

News

• 🖥 A screencast about building a Ticket Vending Machine

An example

1. Use the Rosmaro visual editor to draw a state machine.

2. Write some functional code.

This example makes use of the rosmaro-binding-utils package.

const Frog = handler({
  INTRODUCE_YOURSELF: () => "Ribbit! Ribbit!",
});

const Prince = handler({
  INTRODUCE_YOURSELF: () => "I am The Prince of Rosmaro!",
  EAT: ({action}) => action.dish === 'pizza' ? {arrow: 'ate a pizza'} : undefined
});

3. Enjoy your ({state, action}) => ({state, result}) function!

[
  {type: 'INTRODUCE_YOURSELF'}, // 'I am The Prince of Rosmaro!'
  {type: 'EAT', dish: 'yakisoba'}, // undefined
  {type: 'INTRODUCE_YOURSELF'}, // 'I am The Prince of Rosmaro!'
  {type: 'EAT', dish: 'pizza'}, // undefined
  {type: 'INTRODUCE_YOURSELF'} // 'Ribbit! Ribbit!'
].forEach(action => console.log(
  ({state} = model({state, action})).result.data
));

The complete code of this example can be found on GitHub.

Documentation

• An example
• Building a model
• About drawing Rosmaro graphs
• About writing Rosmaro code

Blog posts

• A JavaScript framework for functions of state and action
• What did we lose when we moved to Redux?
• Dynamic orthogonal regions in state machines
• Decomposing the TodoMVC app with state diagrams
• An overview of the Rosmaro-TodoMVC app codebase
• Testing the TodoMVC app
• State management in JavaScript: data-related state and behavior-related state

Examples

• Bunny App a wizard implemented in Rosmaro, React, Redux and Redux-Saga.
• TodoMVC the famous TodoMVC demo app
• bool-less-todo a todo app implemented without boolean values and without variables

Utilities

• rosmaro-snabbdom-starter - a zero configuration Rosmaro Snabbdom starter.
• rosmaro-redux - connects Rosmaro, Redux and Redux-Saga.
• rosmaro-react - connects Rosmaro and React.
• rosmaro-binding-utils - makes writing simple Rosmaro handlers easier.
• rosmaro-tools - CLI tooling for Rosmaro.
• rosmaro-testing-library - testing utilities for Rosmaro.

License

Rosmaro is licensed under the MIT license.