Inj

Inj is a KISS, require based dependency injector (DI) for node.js

• no monkey patches
• no autowire needed, just use require

Install

To install from npm

npm install inj --save

Getting started

To use Inj, add a single line to any file into which dependencies are injected

// use Inj if container defined, othwerwise use require
require = require('inj')(module, require);

The above line is a noop unless a container is defined. If a dependency is registered with Inj resolve it, otherwise use require.

A container is nothing more than a hash object to contain objects, values and functions later looked up by id.

Application Dependency Injection

Inj starts with no containers. To register app wide dependencies, the root container must first be created and dependencies registered. In practice, the single root container is the only container an app creates. Module specific containers are primarily used in testing.

container.js - Define dependencies

// Create ROOT container and register dependencies
var root = require('inj').getSetRoot();

// $ naming convention emphasizes logical dependencies
root.register('$logger', function(name) { require('logger')(name); });
root.register('$connectionString', 'mysql://foo:password@localhost/db')

app.js - App entry point

require('./container');
require('./store');

store.js - Use DI

require = require('inj')(module, require);

var log = require('$logger')('store');
var connstr = require('$connectionString');
log.log('Connection string', connstr)

model.js - Use DI

require = require('inj')(module, require);

var log = require('$logger')('model');
log.log('Inside model')

Using Depency Injection for Tests

Here's an example of how to mock a built-in module.

reader.js

require = require('inj')(module, require);
var fs = require('fs');
exports.text = fs.readFileSync(__dirname + './file.txt', 'utf8');

readerTest.js

// create module specific container
var inj = require('inj');
var container = inj.create(require.resolve('./reader'));

// register a mock fs
container.register('fs', {readFileSync: function() { return 'foo'; });

// test the module
var a = require('./reader');
assert(a.text, 'foo');

CoffeeScript

CoffeeScript autocreates variable. The statement must be escaped as regular JavaScript with backticks.

`require = require('inj')(module, require)`

MIT License

Copyright (c) 2013 Mario Gutierrez, mario@mgutz.com

See the file LICENSE for copying permission.