kjirou / downspout

A framework to serialize the execution of event handlers for disorderly event emitting

downspout

README: ( English | 日本語 )

A framework to serialize the execution of event handlers for disorderly event emitting

Functions of this module

• Provide a framework for describing event handlers.
• Allow one event handler to execute as transaction processing.
• Queue the execution of event handlers.

Installation

npm install --save downspout

Please use browserify (or webpack) when using with browser.

Usage

Overview

const Downspout = require('downspout');

const state = {
  counter: 0,
};

const useCases = {
  increment: () => {
    return Promise.resolve({
      type: 'INCREMENT',
    });
  },
  decrement: () => {
    return new Promise(resolve => {
      setTimeout(() => {
        resolve({
          type: 'DECREMENT',
        });
      }, 1000);
    });
  },
};

const downspout = new Downspout(useCases);

downspout.on('execution:resolved', ({ result: action }) => {
  switch (action.type) {
    case 'INCREMENT':
      state.counter += 1;
      break;
    case 'DECREMENT':
      state.counter -= 1;
      break;
  }

  process.stdout.write(`${ state.counter }\n`);
});

downspout.execute('increment');  // -> "1"
downspout.execute('increment');  // -> "2"
downspout.execute('decrement');  // -> "1"
downspout.execute('increment');  // -> "2"
downspout.execute('decrement');  // -> "1"

Basic usage by CLI counter samples

• The simplest example
  • Keywords:
    • Use-cases
    • constructor
    • "execution:resolved" event
    • execute
• Wait for completion of asynchronous processing
  • Keywords:
    • Promise
• Pass arguments to use-cases
  • Keywords:
    • Use-case arguments
• Specify the variables on which the use case depends
  • Keywords:
    • context
• Implementation pattern like the Flux
  • Keywords:
    • result
• Runtime error handling
  • Keywords:
    • "execution:rejected" event
    • error
• Runtime error handling for development
  • Keywords:
    • isNoisy
• Constants
  • Keywords:
    • EVENT_NAMES.USE_CASE_EXECUTION_RESOLVED
    • EVENT_NAMES.USE_CASE_EXECUTION_REJECTED
• Fork other use-cases
  • Keywords:
    • utils.fork
• Separate layers of use cases and UI events
  • Keywords:
    • routes
    • dispatch
• Generate bound event emitters to pass any view libraries
  • Keywords:
    • generateExecutor
    • generateDispatcher
• Conclusion: Operable counter
  • Example of the Flux (like) format
• Conclusion: Fizz Buzz Game
  • Example of the MVC format

with the React

(Later)