Skippy

Skippy is designed to be an easy to use, robust, and well tested dependencies container. No magic inside.

What Skippy do

• Instantiate service as described in the dependencies configuration.
• Configure what should be used as service constructor parameters: you can pass another services as reference, parameters, or any values you have configured.
• Manage singleton instance of service (not defined by design pattern, but by configuration).
• Call custom method on service instance to finish it configuration.
• Check the dependencies graph to avoid cyclic dependencies.
• Allowing injection of service mock (only in test environment: NODE_ENV="test").

What Skippy don't do (and never will)

• Introspect JSDoc or parameters name to determine witch service should be inject in a constructor function. You have to define service dependencies in a configuration file.
• Coffee

What Skippy don't do at the moment (maybe one day)

• Manage service scope (allowing private service, who can only be used to instantiate other service, not exposed to the world)
• Use factory service to generate another service (delayed, the post service creation hooks do a part of the job for now)
• Generate a lazy loading proxy function (delayed, until ES6 proxy is well supported)

Installation

npm install --save skippy

Usage

var SkippyFactory = require('skippy').ContainerFactory;

// See configuration section for the configuration details
var services = [/* ... */];
var parameters = {/* ... */}

var container = SkippyFactory.create(services, parameters);

var fooServiceInstance = container.getService('foo');

var barParameterValue = container.getParameter('bar');

container.destroy();

Configuration

Parameters

The parameter configuration format is a simple key/value object:

var foo = "foo value";

module.exports = {
    "parameterName": "parameterValue",
    "foo": foo,
    "bar": 42
}

The parameter name should be a string. The value could be anything.

Services

The services configuration format is an array of individual service configuration:

module.exports = [
    {
        "name": "foo.serviceA",
        "service": require("./ServiceA"),
        "singleton": true
    },
    {
        "name": "foo.serviceB",
        "service": require("./ServiceB"),
        "singleton": false,
        "arguments": [
            "@foo.serviceC"
        ]
    },
    {
        "name": "foo.serviceC",
        "service": require("./ServiceC"),
        "arguments": [
            "%baz%",
            42,
            "@foo.serviceA"
        ]
    },
    {
        "name": "foo.serviceD",
        "service": require("./ServiceD"),
        "arguments": [
            "@foo.serviceA",
            "@foo.serviceB"
        ]
    },
    {
        "name": "foo.serviceD",
        "service": require("./ServiceD"),
        "calls": {
            "setLocale": [
                "@foo.serviceB",
                "%default.locale%"
        ]
    }
];

A service configuration have four possible keys:

• name (string, mandatory): the service name.
• service (function, mandatory): the service constructor function reference.
• singleton (boolean, optional, default true): If true, the service will be a singleton. If false, a new service will be instantiated each time.
• arguments (array, optional, default empty array): An array of the value to inject in the service constructor (see "Arguments" section for more informations).
• calls (object, optional, default empty array): A map of the method to call on the service, each method should have it arguments array (see "Arguments" section for more informations).

Arguments

3 types of arguments type:

• A string like @foo: use another service as argument value (here an instance of the service named foo).
• A string like %baz%: use the corresponding parameter value as argument (here the baz parameter).
• Any other value (scalar, object, function...) will be directly used as an argument.