dependency-injection

Dependency injection with configuration and autowire for node js and browser

npm install dependency-injection
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Dependency injection

Dependency injection with configuration and autowire for node js and browser (for example in combination with simq).

Imagine, that you have got some classes which are used very often. You have got two options: add instance of these classes to window object or to any other object, or create new instance every time when you want to use them.

The problem is that first solution add some "mess" to the window object and the other one is even more problematic. What if you will want to change for example constructor of this class (it's arguments) or call some methods right after class is instanced? Than you will have to change these setups at every place.

But with this package, you can configure your classes at one place and then let's just "ask" for them. (not service locator).

This package is inspired by dependency injection in Nette framework.

Installation

$ npm install dependency-injection

Configuration

Please first read full documentation of easy-configuration. It will really help you.

{
    "services": {
        "application": {
            "service": "path/to/my/application/module",
            "arguments": ["./www", "someOtherVariable"],
            "setup": {
                "setApplicationName": ["nameOfApplication"],
                "setSomethingOther": ["someUselessVariable", "andAnotherOne"]
            }
        }
    }
}

There we set some application service with some arguments which will be given to constructor and some setup. Every time you will need this service, it will have got these arguments and all setup function will be called.

Section service is path for module require (common js).

You can of course use also modules from node_modules directory just like you are used to.

DI automatically look into values from setup in your module (service). If it is function, then it will be called, otherwise argument will be passed into this object property.

Usage

var DIFactory = require('dependency-injection/DIFactory');
var factory = new DIFactory('./path/to/your/configuration/file.json');

var di = factory.create();

Relative paths to config files are supported only on node (not in browser)!!!

This will create new instance of DI class which holding all your services.

You have to also set the basePath property. DI will prepend this basePath to all services' paths from your configuration. So it should be path to root directory of your application.

In example below, you can see how to get your services.

di.get('application');
di.create('application');
di.getFactory('application');

Base path to services

Base path is used for requiring your services. All services (exceptions are node_modules services) are relative to this path.

Default base path is directory in which is your config.json file.

di.basePath = __dirname + '/my/custom/base/directory';

Auto exposing into global

DI can be automatically exposed into window object (when on browser) or into global object (in node). Default name for this object is di.

{
    "setup": {
        "expose": true
    }
}

Custom name:

{
    "setup": {
        "expose": "secondDI"
    }
}

get

Some services may be "singleton" type (not really singleton but with one instance in whole application), which application service is clearly is.

This method will create one instance of service and store it. Every other time, this instance will be returned.

getByPath

Same as get method, but this accepts path to node module (like in your service configuration)

create

Method create will just create new instance of service and will not store it.

getFactory

getFactory is almost the same like create method, but will return anonymous function, so if you then want to use it, you have to call it.

var application = di.getFactory('application');
application = application();        // just call it

Not instantiate services

When you want for example use jQuery as service, you will not want to automatically call something like new jquery. So you can tell DI, that this service will not be instantiate.

{
    "services": {
        "jquery": {
            "service": "jquery"
            "instantiate": false
        }
    }
}

Auto run services

When you are using configuration with json files, you can set some services to be started automatically after calling the create method.

{
    "services": {
        "setup": {
            "service": "./path/to/setup",
            "run": true
        }
    }
}

Autowiring

Accessing some DI object is not so pretty like we want, so there is some nice way how to avoid it. You can let DI to "inject" all your services to other. For example if your application service needs translator service, just let DI to give it to application.

All you need to do is add parameter "translator" to constructor of your application service. This name must be same like name of service in your configuration. DI then automatically give it translator service.

The same thing is also for methods. You don't have to configure them, just set name of needed service in method's arguments and DI will give you these services.

This is quite similar to dependency injection in angular.

Now in most cases you just have to use get method just once for create instance of your base application service and other services will be automatically injected.

Please, try to avoid circular dependencies (service A depends on service B and service B depends on service A).

Examples

In your configuration, you can use three dots as replacement for services.

Services:

var serviceA = function(serviceB, serviceC) { ... };
var serviceB = function(serviceC, namespace, item) { ... };
var serviceC = function(namespace, item, serviceD) { ... };
var serviceD = function() { ... };

Configuration:

{
    "services": {
        "serviceA": {
            "service": "path/to/service/A",
            "instantiate": false
        },
        "serviceB": {
            "service": "path/to/service/B",
            "arguments": ["...", "some namespace", "some item"],
            "instantiate": false
        },
        "serviceC": {
            "service": "path/to/service/C",
            "arguments": ["some namespace", "some item"],
            "instantiate": false
        },
        "serviceD": {
            "service": "path/to/service/D",
            "instantiate": false
        }
    }
}

or more expanded:

{
    "services": {
        "serviceA": {
            "service": "path/to/service/A",
            "arguments": ["..."],
            "instantiate": false
        },
        "serviceB": {
            "service": "path/to/service/B",
            "arguments": ["...", "some namespace", "some item"],
            "instantiate": false
        },
        "serviceC": {
            "service": "path/to/service/C",
            "arguments": ["some namespace", "some item", "..."],
            "instantiate": false
        },
        "serviceD": {
            "service": "path/to/service/D",
            "arguments": ["..."],
            "instantiate": false
        }
    }
}

Only problem is with minified javascript files which changes variable names. Solution for this is write some kind of hint for DI container.

var someFunction = function(otherNameForApplicationService) {
    {'@di:inject': ['@application']};            // services' names are prepended with '@'

    otherNameForApplicationService.run();        // this will call method run on service application
};

or you can also include services by their full paths:

var someFunction = function(otherNameForApplicationService) {
    {'@di:inject': ['$path/to/application/service']};        // services' paths are prepended with '$'

    otherNameForApplicationService.run();
};

or if you need factory:

var someFunction = function(otherNameForApplicationService) {
    {'@di:inject': ['factory:$path/to/application/service']};        // can also be name of service: "factory:@application"

    otherNameForApplicationService.run();
};

These hints has got the same syntax as arguments configuration.

Disable autowiring

If you want to disable autowiring for some service, you can set "autowired" option to false in your config (like instantiate).

When you will try to autowire this service, DI will throw an error.

{
    "services": {
        "setup": {
            "someName": "./path/to/this/service",
            "autowired": false
        }
    }
}

Autowire factories

You can also let DI to autowire factories. For example if you want to get factory for translator, you will add "Factory" to the end of translator.

MyClass.prototype.setTranslator = function(translatorFactory) {
    var translator = translatorFactory();            // now do something with translator
};

When you have got for example foreign library registered as service in this DI and want to autowire some other service into it, you have to use their names of methods arguments.

Another possibility is to set these services in your config.

{
    "services": {
        "foreignLibrary": {
            "service": "path/to/service",
            "arguments": [
                "@translator"
            ]
        }
    }
}

or with full module path:

{
    "services": {
        "foreignLibrary": {
            "service": "path/to/service",
            "arguments": [
                "$path/to/translator/module"
            ]
        }
    }
}

you can even access properties or methods from other services:

{
    "services": {
        "foreignLibrary": {
            "service": "path/to/service",
            "arguments": [
                "@translator::getLanguage('en')",            // en can be default language
                "@http::basePath"
            ]
        }
    }
}

or create service from other service (for example from factory)

{
    "services": {
        "httpFactory": {
            "service": "./path/to/http/module"
        },
        "http": {
            "service": "@httpFactory::createHttp()"
        }
    }
}

Default settings

You can change default behavior of some options in your config file.

{
    "defaults": {
        "instantiate": false
    },
    "services": { ... }
}

Default services

There are already prepared some services.

  • di: di container itself
  • timer: object with setTimeout, setInterval, clearTimeout and clearInterval methods
  • window: window object (browser only)
  • document: window.document object (browser only)
  • global: global object (node.js only)
di.get('di');

Parameters

In documentation of easy-configuration you can see that you can use also parameters. This is useful for example for setting your services.

{
    "parameters": {
        "database": {
            "user": "root",
            "password": "toor"
        }
    },
    "services": {
        "database": {
            "service": "database/connection",
            "arguments": [
                "%database.user%",
                "%database.password%"
            ]
        }
    }
}

Credentials for database connection will be root and toor.

Or you can access these parameters from di object.

console.log(di.parameters);                            // whole object of expanded parameters
console.log(di.getParameter('database.user');        // root

getParameter() method is just shortcut to getParameter method in easy-configuration.

Advanced configuration

If you need more control over configuration, you can create instance of easy-configuration object on your own and pass it to DIFactory.

var Configuration = require('dependency-injection/Configuration');        // shortcut to easy-configuration module
var DIFactory = require('dependency-injection/DIFactory');

var config = new Configuration;
config.addConfig('./path/to/config.json', 'development');

var factory = new DIFactory(config);
var di = factory.create();

Without configuration

Maybe it will be better for someone to use this DI without configuration, so here is example of application, translator and jquery definition.

var DI = require('dependency-injection');
var di = new DI;

di.addService('application', require('./path/to/my/application/module'), ['./www', 'someOtherVariable'])
    .addSetup('setApplicationName', ['nameOfApplication'])
    .addSetup('setSomethingOther', ['someUselessVariable', 'andAnotherOne']);

di.addService('translator', require('./path/to/translator'))
    .addSetup('setLanguage', ['en']);

di.addService('jquery', 'jquery')
    .setInstantiate(false);

di.addService('private', 'my/private/service')
    .setAutowired(false);

Instead of path to service (second parameter in addService method) you can also use string with path, but this path will be then relative to class of DI!

Create instance

If you have got some other object which you want to use with other services, but can not use configuration or DI for this, you can use createInstance method and DI will create new instance of your object with dependencies defined in constructor.

var SuperClass = require('./mySuperClass');
var super = di.createInstance(SuperClass, ['and some argument']);

Inject method

For simple injecting services into your functions, you can use method inject.

di.inject(function(application) {
    application.doSomeMagic();
});

or with arguments

di.inject(function(application, path) {
    application.setPath(path);
}, ['...', '/path/to/some/folder']);        // syntax is same like in configuration

you can of course use also autowire hints.

Tests

$ npm test

Changelog

  • 2.3.0

    • Added option for services derived from other services
    • Support for calling methods from other services in config
    • Some optimization
    • exposed easy-configuration into dependency-injection/Configuration
    • DIConfigurator renamed to DIFactory (DIConfigurator is now deprecated)
    • Support for services from npm modules
    • Default base path for services in config file is dir name of config file
    • Updated dependencies
  • 2.2.0

    • Relative paths to config files
    • Little updates in tests
    • Added default services
    • Better documentation
    • Many improvements in configuration (see easy-configuration)
  • 2.1.1

    • Hints has exactly the same syntax as arguments configuration
    • Inject method's second argument is args, not scope (BC break!)
  • 2.1.0

    • Added config object do DIFactory
    • Bug with exposing
    • Accessing parameters from di instance
    • Updated dependencies
  • 2.0.1

    • Injecting by arguments and hints was not working
  • 2.0.0

    • Removed autowiring into inject methods (BC break!)
    • Added methods getByPath and getFactoryByPath
    • Added basePath option
    • Better docs
    • Added hints for autowiring
  • 1.8.0

    • Better tests (mocha does not need to be installed globally)
    • Updated dependencies
    • Added badges
    • Added to travis
  • 1.7.3

    • Bug with no-string arguments
  • 1.7.2

    • Bug with functions as services
  • 1.7.1

    • Potential bug in IE
  • 1.7.0

    • Updated dependencies
    • Added injectMethods to services
    • Refactored autowiring
    • Some optimizations
    • DI.autowireArguments moved to Helpers.autowireArguments
    • Throwing an error if circular reference is found
  • 1.6.6 - 1.6.7

    • Bugs in Internet Explorer 8
  • 1.6.2 - 1.6.5

    • Some optimizations
    • Should assert module replaced with chai
    • Better error messages
  • 1.6.1

    • Bug with setting other arguments than strings
  • 1.6.0

    • Added get method, getByName is now deprecated
    • Added inject method
    • Autowiring with @
  • 1.5.2

    • Add setup into properties
  • 1.4.1

    • Bug
  • 1.4.0

    • Option for exposing di into
  • 1.3.2 - 1.3.3

    • Bug with run option
  • 1.3.1

    • Just some mistake in readme
  • 1.3.0

    • Added auto run option into configuration
    • Really huge mistake in readme
  • 1.2.3

    • Autowiring parameters even if they are not in function definition
  • 1.2.2

    • Added missing test
  • 1.2.1

    • Added ability to inject DI container itself
  • 1.2.0

    • Added DI.createInstance method
    • DI.addService accepts also objects
    • Typos in README
    • Optimizations
    • Added mocha tests
    • Added setInstantiate method
    • Added autowired option
  • 1.1.1

    • inject methods are called before custom setup
  • 1.1.0

    • Support for not-instantiate services
  • 1.0.1

    • Added information about autowiring factories
  • 1.0.0

    • Initial version
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