minidi

Minimal, convention-based, inversion-of-control/dependency injection for Node.js. Originally written for Appraise.

Designed to work with minimal impact on client code and make unit testing easy.

Features

• loads components lazily/on demand
• easy, convention based access to components -- just ask for a property passed into the constructor
• minimal impact on your code -- requires components only to have a specific constructor/function parameters
• no external dependencies
• production-ready, tested
• supports any Node module as a component, including NPM/Node packages and local files
• supports primitive objects as components

Limitations

• all components are initialised at most once
• does not support cyclic dependencies

Install from NPM

npm inistall minidi

Usage

For a quick example, check out the Example Project. Run node main.js in the example directory to see it in action.

Component syntax

Each component should have a constructor with a single argument, a key-value map for the configuration. The component can access other components or any generic configuration passed to the component builder simply by accessing properties of the configuration. MiniDi will dynamically instantiate components as they are needed.

For unit testing purposes, instantiate the component class directly and pass mock collaborators or test stubs into the second argument.

module.exports = class Sender {
  // constructor for components receives all other components
    constructor(config) { 
    // just ask for a component by name, it will be lazily-initialised if required
        this.receiver = config.receiver; 
    }
    send(message) {
        this.receiver.receive(message);
    }
};

Initialising the container

Create a new instance of minidi and pass in two arguments: component objects and component modules.

• component objects are literal values (eg config properties, strings, arrays or objects you already initialised)
• component modules are a key-value map of component names to module names. You can use Node module names or file paths. If you want to use local files instead of package dependencies/Node module names, remember to use __dirname to ensure that local paths are resolved based on the current file, for example path.join(__dirname, 'sender').

Just access any component directly as a property of the container instance, using the name from the components map.

const MiniDi = require('minidi'),
  path = require('path'),
  // static properties to pass into components
  config = { 
    name: 'Tom' 
  },
  // dynamic components to instantiate
  modules = {
    //keys are component names
    //values are module names or local file paths with
    sender: 'some-node-module',
    receiver: path.join(__dirname, 'receiver')
  },
  minidi = new MiniDi(config, modules);
 
minidi.singer.sing(/*... */); // just access a component by property name

Author

Gojko Adzic

License

MIT, see the License