injektor

With injektor (and almost of dependency injection libraries), a developer can manage the service objects in a common "place" called container and doesn't care about assigning the dependent parameters to a service when it is invoked.

Usage

Installation

Install injektor module:

$ npm install --save injektor

Example

In your program, create the container:

var Injektor = require('injektor');
var injektor = new Injektor();

Register an object or define a service with some dependencies as follows:

injektor
  .registerObject('greeting', {
    greet: function() {
      return 'Hello world!';
    }
  });

injektor
  .defineService('service1', function(fullname) {
    var self = fullname;
    this.sayHello = function(name) {
      console.log('Hello ' + name + ". I'm " + self);
    }; 
  })
  .registerObject('fullname', 'Computer');

injektor
  .defineService('service2', function() { 
      this.sayWellcome = function(name) {
        console.log('Wellcome to ' + name);
    }; 
  });

Uses the lookup() method to get services or invoke() method to evaluate the services:

injektor.lookup('service1').sayHello('Ubuntu');

injektor.invoke(function (greeting, service1, service2) {
    console.log(greeting.greet());
    console.log('\n');
    service1.sayHello('Injektor');
    service2.sayWellcome('Vietnam');
});

The console will display the text below:

Hello world!
Hello Injektor. I'm Computer
Wellcome to Vietnam

API

Constructor

new Injektor(args)

args can be:

• args.detectCyclicDependencies - enables/disables dependency cycle detection (default: true).
• args.nameResolvingStrictMode - enables/disables name resolving strict mode (default: false).
• args.allowLookupDuplicateNames - allows to return the fisrt matching name of duplicate short names (default: false).
• args.separator - delimiter character (default: /).

Example:

var Injektor = require('injektor');
var injektor = new Injektor({
  separator: ':'
});

Methods

injektor.defineService(name, constructor, opts)

Method defineService() registers a service name with its constructor. The parameters include:

• name - a case-sensitive string that presents the name of the defined service. The name must contain only letters, digits and underscore characters. It must start with a letter.
• constructor - a function that is used with the new operator to create a new object. This object is cached by injektor and returned by lookup().
• opts.scope - a namespace of the scope in which this service/object belongs to.
• opts.exceptions - a reference to an empty array that will collect thrown exceptions (if any) and prevent function crack.

Method defineService() returns the injektor object itself.

injektor.registerObject(name, valueOrObject, opts)

Method registerObject() registers an object or a value (number, boolean, null,...) with its name. The parameters are similar to defineService() method, excepts the second parameter is a value or an object. It also returns the injektor object.

injektor.lookup(name, opts)

Method lookup() instantiates a service with injected dependencies into object, caches it for the next use, and returns it. This method contains the following parameters:

• name - the name of a service or an object that should be retrieved.
• opts.scope - a namespace of the scope in which this method finds the service or the object (default: undefined).
• opts.exceptions - similar to defineService() method (default: undefined).

injektor.invoke(name_1, ..., name_n, callback)

Method invoke() retrieves an array of services or objects that are identified by name_1, ..., name_n, and push them as the parameters to the callback function. This method will return the callback's returned value.

Dependency Annotations

Object schema annotation

var Injektor = require('injektor');
var injektor = new Injektor();

var MyResource = function(params) {
  params = params || {};
  var fullname = params.fullname;
  var document = params.document;
  
  this.process = function(action) {
    console.log('The developer %s will %s the document %s', 
        fullname, action, JSON.stringify(document));
  };
};

MyResource.argumentSchema = {
  "type": "object",
  "properties": {
    "fullname": { "type": "string" },
    "document": { "type": "object" }
  }
};

injektor
  .defineService('myResource', MyResource)
  .registerObject('fullname', 'Peter Pan')
  .registerObject('document', { 
    type: 'Book',
    content: 'Peter and Wendy'
  });

injektor.lookup('myResource').process('open');

The console will display the following text:

The developer Peter Pan will open the document {"type":"Book","content":"Peter and Wendy"}

Object properties annotation

var Injektor = require('injektor');
var injektor = new Injektor();

var MyResource = function(params) {
  params = params || {};
  var fullname = params.fullname;
  var document = params.document;

  this.process = function(action) {
    console.log('The developer %s will %s the document %s',
        fullname, action, JSON.stringify(document));
  };
};

MyResource.argumentProperties = [ "fullname", "document" ];

injektor
  .defineService('myResource', MyResource)
  .registerObject('fullname', 'Peter Pan')
  .registerObject('document', {
    type: 'Book',
    content: 'Peter and Wendy'
  });

injektor.lookup('myResource').process('open');

The console will display the following text:

The developer Peter Pan will open the document {"type":"Book","content":"Peter and Wendy"}

Explicit name annotation

var Injektor = require('injektor');
var injektor = new Injektor();

injektor
  .defineService('recipe', ['steps', 'object',
    function(steps, object) {
      steps = steps || [];
      this.action = function(name) {
        console.log('Hello, the instruction of %s is:', name);
        steps.forEach(function(step) {
          console.log(' - %s the %s', step, object);
        });
      };
    }
  ])
  .registerObject('steps', [
    'clean', 'boil', 'peel', 'eat'
  ])
  .registerObject('object', 'Eggs');

injektor
  .invoke(['recipe', function(rp) {
    rp.action('Peter Pan');
  }]);

Implicit name annotation

var Injektor = require('injektor');
var injektor = new Injektor();

injektor
  .defineService('recipe', function(steps, object) {
    steps = steps || [];
    this.action = function(name) {
      console.log('Hello, the instruction of %s is:', name);
      steps.forEach(function(step) {
        console.log(' - %s the %s', step, object);
      });
    };
  });

injektor
  .registerObject('steps', [
    'clean', 'boil', 'peel', 'eat'
  ])
  .registerObject('object', 'Eggs');

injektor.lookup('recipe').action('Peter Pan');

License

MIT