SDIC: Simple Dependency Injection Container

Dependency injection container with auto injection of module dependencies (by parameter names).

Prerequisites

Node.js version >= 6.0

Install

npm install sdic

Container initialization

const container = require('sdic').create();

or

import sdic from 'sdic';
const container = sdic.create();

Container API

load(path, opts = {})

Loads single module file or all module files in given path.

• path - path to module file or folder with modules
• opts - options
  • alias - module alias (for a single file module) or a basedir alias (for a folder of modules)
  • cache - keep instances of modules is cache? (default: true)
  • tags[] - list of tags for loaded module(s)
  • recursive - recursive loading of folder (default: true)
  • filter - loads only modules by regexp filter
  • ignore[] - list of regexp to ignore unwanted modules
  • reverseName - create a module name "up to down" (default: false)
  • prefix - prefix module name
  • postfix - postfix module name
  • deduplicate - remove multiple same string occurences (default: false)
  • uppercaseFirst - create a module name with uppercased first letter (default: false - module name starts with lowercased letter)
  • isConstructor - loaded module is a constructor, load and return it as a constructor, do return an instances (default: false - modules as singletons by default)

register(name, fn, opts = {})

Registers a single module.

• name - module name
• fn - module body (function, JSON, primitive, ...)
• options - see above

has(name)

Checks whether container contains given module by name.

get(name, overrides)

Returns registered module from container.

• name - registered module name
• overrides - collection of overridden module dependencies

getAll()

Returns all registered modules

getByTag(tag)

Returns all registered modules with given tag.

• tag - tag name

override(name, fn, opts)

Overrides registered module with new instance. Parameters: see register method

unregister(name)

Unregisters module from container.

• name - module name to unregister

clear()

Removes all modules from container.

Tutorial

Module definition - a module with no dependencies

module.exports = (/* no dependencies */) => {
    // module instance
    return {
        someMethod: () => {}
    }
}

or using ES6 export default syntax:

export default (/* no dependencies */) => {
    // module instance
    return {
        someMethod: () => {}
    }
}

Module definition - a module with some dependencies

// module depends on myDb and myNextService
module.exports = (myDb, myNextService) => {
    // module instance
    return {
        someMethod: () => {
            return myNextService.doSomething(myDb.getWhatever());
        }
    }
}

or using ES6 export default syntax:

// module depends on myDb and myNextService
export default (myDb, myNextService) => {
    // module instance
    return {
        someMethod: () => {
            return myNextService.doSomething(myDb.getWhatever());
        }
    }
}

Multiple modules definition using ES6 named exports

// module without dependencies
export const firstFunctionalService = () => {
    return {
        method: () => ({passed: true})
    }
};

// module dependds on fooService
export function secondFunctionalService (fooService) {
    return {
        method: () => fooService.method()
    }
};

// module dependds on fooService
export class ClassService {
    constructor(fooService) {
        this.fooService = fooService;
    }

    method() {
        return this.fooService.method();
    }
}

ES6 note: container returns instances of modules by default (aka singletons). If you want to register a class (constructor function), you have to use option: isConstructor: true

class FooBar {}
container.register('FooBar', FooBar);
container.get('FooBar'); // --> returns an instance of FooBar (default behaviour)

class FooBar {}
container.register('FooBar', FooBar, {isConstructor: true});
container.get('FooBar'); // --> returns class FooBar

// all modules will be loaded as constructors
container.load('/path/to/constructors_folder', {isConstructor: true});

Manual module registration

container.register('myJson', {foo: 'bar'});
container.get('myJson'); // returns {foo: 'bar'}

container.register('myPrimitive', 123);
container.get('myPrimitive'); // returns 123

container.register('myDep', (/* no dependencies */) => {
    return {
        doWhatever: () => {return 'whatever'}
    }
});

container.register('myModule', (myJson, myPrimitive, myDep) => {
    return {
        getAll: () => ({myJson, myPrimitive, myDepValue: myDep.doWhatever()})
    }
});
container.get('myModule'); // returns an instance of module with injected dependencies

Flat structure loading

Consider this project structure:

    + config.json
    |
    + services/
    + - users.js
    + - user-roles.js
    |
    + repositories/
    + - roles.js
    + - users.js
    |
    + lib/
    + - validator.js

Let's load all files into SDIC.

container.load('./config');  // loads single file: config.json
container.load('./services');  // loads all files in "services" folder (basedir == "services")
container.load('./repositories');  // loads all files in "repositories" folder (basedir == "repositories")
container.load('./lib');  // loads all files in "lib" folder (basedir == "lib")

By default, all loaded modules will be named "down to up": camelCased filename + camelCased basedir. So the module names will be:

• config
• userRolesServices
• usersServices
• rolesRepositories
• usersRepositories
• validatorLib

The "plurals" sounds strange. We can rename the basedirs to "singular" or tweak the loader a little bit:

container.load('./config');  // this is OK, keep it
container.load('./services', {alias: 'service'});  // alias basedir as "service"
container.load('./repositories', {alias: 'repository'});  // alias basedir as "repository"
container.load('./lib', {alias: null});  // ignore basedir name, there's no need to have explicit "Lib" postfix

Now the module names will be:

• config
• usersService
• userRolesService
• rolesRepository
• usersRepository
• validator

Nice :-)

Nested structure loading

Now consider more nested project structure:

    + services/
    + - users/
    + -- roles.js
    + -- users.js
    |
    + repositories/
    + - users/
    + -- roles.js
    + -- index.js

We'll skip "config" file and "lib" folder (see above). Let's load all files into SDIC.

container.load('./services');  // loads all files in "services" folder (basedir == "services")
container.load('./repositories');  // loads all files in "repositories" folder (basedir == "repositories")

By default, all loaded modules will be named "camelCased, down to up": filename + subfolders + basedir. So the module names will be:

• usersUsersServices
• rolesUsersServices
• indexUsersRepositories
• rolesUsersRepositories

Sounds really strange. Let's set up the loading better. The "services" folder first. It'd be cool to start the name with the subfolder (if any), then the filename and the basedir at the end.

container.load('./services', {
    alias: null,        // disable basedir name at the beginning
    reverseName: true,  // name will be generated "up to down"
    postfix: 'service', // instead of basedir as prefix, append it at the end
    deduplicate: true   // removes multiple "users" string ("users" folder + "users" file)
});

Now the modules will be:

• usersService
• usersRolesService

Better, but still sounds strange because of "plurals". To fix this we need to split the loading into two steps:

container.load('./services/users', {  // the basedir is now "users"
    alias: 'user',      // alias basedir as "user"
    postfix: 'service', // append "service" at the end
    ignore: [/users\.js/] // ignore users.js file for now
});
container.load('./services/users/users', {alias: 'userService'}); // append the ignored file

Finally the modules will be:

• userService
• userRolesService

We can load the "repositories" folder the same way.

ES6 note: when loading named exports into the container, then:

• exported name will be taken instead of a filename (with lowercased first letter)
• filename will be taken for default (not-named) export

Minification

SDIC supports code minification. Because module dependencies are defined using parameter names, the code minification process would damage them (to a, b, c, ... etc.) and SDIC would not be able to load them properly. To prevent this situation all you need to do, is to define the list of a module dependencies in a property dependencies:

ES6 modules dependencies

const service = (a, b) => { // minified param names
    return {
        method: () => a.method() + b.method()
    };
};
service.dependencies = ['fooService', 'barService']; // <--- definition of dependencies

export default service;

CommonJs modules dependencies

const service = (a, b) => { // minifies param names
    return {
        method: () => a.method() + b.method()
    };
};
service.dependencies = ['fooService', 'barService']; // <--- definition of dependencies

module.exports = service;

Class dependencies

export class ClassService {
    constructor(a, b) { // minified param names
        this.fooService = a;
        this.barService = b;
    }

    method() {
        return this.fooService.method() + this.barService.method();
    }
}
ClassService.dependencies = ['fooService', 'barService']; // <--- definition of dependencies

TODO

• load both file and folder with the same name, eg:

   +- users/ <- load this
   +- -- foo.js
   +- users.js <- as well as this

• docs, docs, docs

Based on the idea of: https://www.npmjs.com/package/adctd