di-lite

di-lite.js

di-lite is designed to act as a minimalistic dependency injection container in Javascript. It has no dependency on any other framework such as CommonJs or RequireJs in contrary to some of other more heavy weight DI container implementation on the web.

Use Cases

di-lite was initially extracted from a Backbone.js based application. In this application, RequireJs was used to wire dependencies at module level. Each module could contain multiple views and models. We found using RequireJs to wire every individual view and model is a bit of overkill and verbose, however we still want the inversion of control to keep our code nicely isolated and testable. That's the reason behind the creation of this lightweight container implementation - to provide dependencies injection at sub-modular level.

That being said di-lite is designed to be used standalone there is no dependency on Backbone or RequireJs. Its a fully functional dependency injection container by itself while extremely lightweight and works well both in browser or node.

Install with npm

npm install di-lite

Install without npm

Download

• di-lite

How-to Guide

• Basic Wiring
• Wiring with Assignment
• Passive Dependency Resolution
• Singleton By Default
• Prototype Strategy
• Passing Constructor Arguments
• Cyclical Dependency
• Functional Object
• Lifecycle Hook
• Runtime Dependencies Override
• Create Your Own

Basic Wiring

var A = function(){
    ...
    this.dependencies = "b, c";
    ...
};
var B = function(){
    ...
    this.dependencies = "c";
    ...
};
var C = funciton(){...};
 
// create di context
var ctx = di.createContext();
 
// register a class with an unique name
ctx.register("a", A);
ctx.register("b", B);
ctx.register("c", C);
 
// initialize di container so all singleton(default) objects will be wired at this stage
ctx.initialize();
 
var instanceOfA = ctx.get("a");
instaceOfA.b === ctx.get("b"); // true
instaceOfA.c === ctx.get("c"); // true
 
var instanceOfB = ctx.get("b");
instanceOfB.c === ctx.get("c"); // true

Wiring with Assignment

By default dependencies are wired using their registered name respectively, however you can override this behavior by including an explicit assignment in dependency definition. You can also mix both explicit and implicit assignment in dependency definition.

var A = function(){
    ...
    this.dependencies = "bee=b, c"; // mix explicit and implicit assignment
    ...
};
 
ctx.initialize();
 
var instanceOfA = ctx.get("a");
instaceOfA.bee === ctx.get("b"); // true - explicit assignment
instaceOfA.c === ctx.get("c"); // true - implicit assignment

Passive Dependency Resolution

di-lite container resolves dependency passively on demand when get() method is invoked. It only tries to resolve dependency for this particular object thus only traverse its sub-dependency-tree. initialize() call does resolve all dependencies for all registered objects however it is actually optional (though recommended to guarantee).

ctx.register("a", A);
ctx.get("a"); // this triggers the dependency resolution for "a" alone
ctx.initialize(); // this triggers the dependency resolution for everyone registered

Singleton By Default

All objects created and managed by di-lite.js container are by default singleton.

ctx.get("a") === ctx.get("a"); // true

Prototype Strategy

If you want container to create a new instance of your class each time you invoke get method then you need to configure your registration with di.strategy.proto cache strategy.

ctx.register("prototype", A).strategy(di.strategy.proto);
ctx.get("prototype") === ctx.get("prototype"); // false
ctx.create("prototype", 100); // create can be used if you want to explicitly pass in a new parameter

Passing Constructor Arguments

You can pass arguments to constructor function by using the additional parameter in register call.

ctx.register("str", String, "hello world"); // signle simple argument
ctx.register("profileView", ProfileView, {el: "#profile_div"}); // signle object literal argument
ctx.register("array", Array, ["Saab","Volvo","BMW"]); // multiple argument is passed in using an array

Cyclical Dependency

di-lite.js container supports solution of cyclical dependencies, so the following dependency relationship is valid.

var A = function(){
    ...
    this.dependencies = "b";
    ...
};
var B = function(){
    ...
    this.dependencies = "a";
    ...
};
 
ctx.register("a", A);
ctx.register("b", B);
 
ctx.initialize();
 
ctx.get("a").b === ctx.get("b"); // true
ctx.get("b").a === ctx.get("a"); // true
ctx.get("a").b.a === ctx.get("a"); // true
ctx.get("b").a.b === ctx.get("b"); // true

Functional Object

What if your are using functional object pattern and do not have a constructor function for your object? di-lite.js fully supports functional object pattern since we believe this is the best way to create javascript object anyway.

var FuncObject = function(spec){
    var that = {};
    ...
    return that;
};
 
ctx.register("funcObjSingleton", FuncObject, spec).factory(di.factory.func);
 
// function chaining can be used to customize your object registration
ctx.register("funcObjProto", FuncObject, spec)
    .strategy(di.strategy.proto)
    .factory(di.factory.func);
 
ctx.initialize();
 
ctx.get("funcObjSingleton"); // will return you a signleton instance of FuncObject
ctx.get("funcObjProto"); // will return you a new instance of FuncObject each time

Lifecycle Hook

di-lite container provides a lifecycle hook callback ready if the wired object provide a ready function then the callback will be executed once all dependencies are satisfied.

var MyView = Backbone.View.extend({
    ...
    dependencies: "otherView, myModel",
    ready: function(){this.render();} // called once all dependencies are satisfied
    ...
});

Runtime Dependencies Override

What if I need to provide different dependencies different instances of the same class?

ctx.register("a", A)
    .dependencies("bee=b"); // dependencies specified here will take precedence
...
ctx.get("a").bee === ctx.get("b"); // true

Create Your Own

Sometimes you just don't have control over the object you want to wire or maybe you need to create the object and initialize before anything else is create or even registered. You can manually insert object into di-lite container and control the whole creation process this way.

ctx.register("history").object(Backbone.history);
...
ctx.get("history").start(); // you can use it since it is already created and initialized
...
ctx.initialize(); // initialize the rest of the objects

How to build di-lite locally

Prerequisite modules

Make sure the following packages are installed on your machine

• node.js
• npm
• apache ant

Install dependencies

di-lite$ npm install

Build and Test

di-lite$ ./make

License

di-lite is an open source javascript library and licensed under Apache License v2.