Idioc NPM | npm.io

idioc

Angular-like dependency injection helper for Node.js.

Usage

First of all, register your modules in the container. It is recommended to move the configuration to a separate module.

// myioc.js
module.exports = require('idioc').register({
    myService: 'path/to/my/service',
    myStorage: 'path/to/my/storage',
})

Let's say we have a service myService which is depends of storage myStorage and is able to retrieve some data using the storage's API:

// myservice.js
module.exports = function(myStorage) {
    return {
        getSomeData: function(params, cb) {
            myStorage.getSomeDataFromSomewhere(params, cb)
            return this
        }
    }
}

Note that we don't need to directly require our storage module - it will be injected into the service automatically. It is also means that you can easily mock the service when running tests, e.g. using NODE_ENV switch in container configuration:

// myioc.js
var env = process.env.NODE_ENV || 'development'

module.exports = require('idioc').register({
    myService: 'path/to/my/service',
    myStorage: env === 'test' ? 'path/to/mock/storage' : 'path/to/my/storage',
})

Okay, now we need to implement the storage. Let's say it uses Mongoose to retrieve data from MongoDB database. How do we inject core/vendor modules (those from ./node_modules or /usr/lib/node_modules or whatewer)? Just prefix dependency name with $ symbol and it will be threated as a vendor module:

// mystorage.js
module.exports = function($mongoose, $underscore) {
    return {
        getSomeDataFromSomewhere: function(params, cb) {
            $mongoose.model('SomeData').find(params, function(err, data) {
                if (err) { cb(err); return }
                // Make underscore to do something.
                // (It is for the sake of example, don't try that at home.)
                var transformedData = $underscore.pluck(data, ['firstname'])
                cb(null, transformedData)
            })
            return this
        }
    }
}

Kinda OK, but we're forced to use these ugly names like $mongoose and $underscore. Where's my short and cool _.pluck()? No problem, use the long form of injection:

// mystorage.js
module.exports = ['$mongoose', '$underscore', function(mongoose, _) {
    return {
        getSomeDataFromSomewhere: function(params, cb) {
            mongoose.model('SomeData').find(params, function(err, data) {
                // . . .
                var transformedData = _.pluck(data, ['firstname']) // Yay!
                cb(null, transformedData)
            })
            return this
        }
    }
}]

Finally, the application module itself, which uses myService to do stuff:

// myapp.js
var myioc = require('./myioc'), // Config first.
    myService = myioc('myService')

// That's all - myService is here with all its deps injected.
myService.getSomeData({...params...}, function(err, data) {
    // Take your data (or error - shit happens).
})

Or inject the service into anonymous module, it is fine too:

// myapp.js
var myioc = require('./myioc')

myioc.inject(function(myService) { // Long form is available here too.
    myService.getSomeData({...params...}, function(err, data) {
        // . . .
    })
})