# white-horse [![Build Status](https://travis-ci.org/scravy/white-horse.svg?branch=master)](https://travis-ci.org/scravy/white-horse) [![Dependencies](https://david-dm.org/scravy/white-horse.svg)](https://david-dm.org/scravy/white-horse#info=dependencies&view=table) [![Dependencies](https://david-dm.org/scravy/white-horse/dev-status.svg)](https://david-dm.org/scravy/white-horse#info=devDependencies&view=table) Simple, light-weight dependency injection for NodeJS that supports modules which load asynchronously. ## Usage npm install white-horse ```JavaScript var WhiteHorse = require('white-horse'); var container = new WhiteHorse(require, { /* options (optional) */ }); ``` ## Examples ```JavaScript WhiteHorse(require) .register('oneModule', function () { return "l"; }) .register('anotherModule', function (oneModule, yetAnotherModule) { return "He" + oneModule + yetAnotherModule; }) .register('yetAnotherModule', function (oneModule, $done) { $done(null, oneModule + "o"); }) .inject(function (anotherModule) { console.log(anotherModule); // prints "Hello" }, function (err) { console.error(err); }); ``` ```JavaScript WhiteHorse(require) .use(require('./package.json')) .scan('modules', function (main) { main.run(); }, function (error) { console.log("Aww snap:", error); }); ``` ## API ### `register(name, module)` Registers a `module` with the given `name`. The dependencies of that factory function are its named arguments or the dependencies you name explicitly using `$dependencies = [ ... ]`. A module can be anything: ```Javascript container.register('pi', Math.pi) container.get('pi', function (err, module) { console.log(module); // 3.141592653589793 }); ``` If it is a function it is taken to be the factory for a singleton. Note how `module` does have the same value when retrieving the module twice: ```JavaScript function f() { return 7 + Math.random(); } container.register('seven', f); container.get('seven', function (err, module) { console.log(module); // 7.9937735903076828 }); container.get('seven', function (err, module) { console.log(module); // 7.9937735903076828 }); ``` If you want to use the literal function, set `$factory = false` on it. Note how `module()` is a function invocation in the following example: ```JavaScript function g() { return Math.random(); } g.$factory = false; container.register('func', g); container.get('func', function (err, module) { console.log(module()); // 0.44126248732209206 console.log(module()); // 0.18552138609811664 }); ``` If you do not want it to be a factory for a singleton, set `$singleton = false` on it. Node how the `module` has a different value each time it is retrieved: ```JavaScript function h() { return Math.random(); } h.$singleton = false; container.register('singleton', h); container.get('singleton', function (err, module) { console.log(module); // 0.5290916324593127 }); container.get('singleton', function (err, module) { console.log(module); // 0.6509554286021739 }); ``` If a function fails to initialize a module, the callback will report that exception: ```JavaScript function e() { throw "damn it"; } container.register('exceptional', e); container.get('exceptional', function (err, module) { console.log(err); // "damn it" (would be `null` on success) }); ``` ### `get(name, callback)` Retrieves an instance of the module named `name`. Example: ```JavaScript container.get('module', function (err, instance) { if (err) { // report `err` } else { // do something with `instance` } }); ``` ### `use(npmModule)` Uses the given `npmModule`. Example: ```JavaScript container.use('nodash'); container.inject(function (nodash) { // `nodash` is the same as `require('nodash')` // but this way it is injected. }); ``` ### `useAs(npmModule, alias)` Uses the given `npmModule` but registers it with the given `alias`. Example: ```JavaScript container.useAs('nodash', 'theDash'); container.inject(function (theDash) { // ... }); ``` ### `scan(directory, onSuccess, onError)` Scans the given `directory` and injects the `onSuccess` function. On any error while scanning or injecting `onError` is called. If `onError` is not a valid callback it will emit the `unhandled_error` event. ### `inject(function, callback)` Injects the given `function` in this containers context. ```JavaScript container.register('a', 1); container.regsiter('b', 2); container.inject(function (a, b) { console.log(a + b); // 3 }); ``` ### `injectWith(function, dependencies, callback)` Injects the given `function` with the given array of `dependencies`. ```JavaScript container.register('a', 1); container.register('b', 2); function f() { console.log(arguments[0]); console.log(arguments[1]); } container.injectWith(f, [ 'a', 'b' ]); // 1 \n 2 \n ``` ## Options ### `usePackageJson` (boolean, default: true) Whether `dependencies` from your `package.json` should automatically be picked up or not. With this option, if your `package.json` contains `nodash` as a dependency, you can inject `nodash` without registering it by the means of `container.use('nodash')`. It is enabled by default. ### `autoRegister` (array of strings) An array of modules which should automatically be registered. By default this is a list of all the modules which are built-in to node (like `path`, `fs`, etc.). If you do not want any modules to be registered automatically just set this to `[]` (the empty array). By default you can inject the modules that ship with node without explicitly registering them, i.e. ```JavaScript container.inject(function (fs, path) { // ... }); ``` will work without the need of explicitly doing `container.use('fs')` or `container.use('path')` first. If you want to disable or change this behavior, you can set this option to a custom array, for example: ```JavaScript new WhiteHorse(require, { autoRegister: [] }); ``` ### `npmPrefix` (string) ### `npmPostfix` (string) ### `npmNormalize` (boolean) When `true` will normalize all npm module names loaded from `package.json` so that a module like `hello-world-123` could be loaded by the name `helloWorld123`. This is primarily useful when auto registering modules and using their names in function declarations directly (otherwise modules like these would have to be mentioned in a `$dependencies` declaration). By default `false`. ### `npmNameTransformer` (function: string -> string) ## Magic Modules ### `$root` The path to your project root, determined from the `require` method which you passed into the `WhiteHorse` constructor. ### `$module` The name of the module this instance is going to be injected into. A factory which has `$module` as one of its dependencies is automatically regarded as `$singleton = false`, i.e. it will be invoked everytime the module it is registered as is injected somewhere. ```JavaScript container.register('magic', function ($module) { return $module; }); container.register('a', function (magic) { console.log(magic); // "a" }); container.register('b', function (magic) { console.log(magic); // "b" }); ``` `$module` is useful when building plugins. As an example: [white-horse-config](http://github.com/scravy/white-horse-config) is using this mechanism to inject per-module configuration. ### `$done` A callback to finish loading of the module. If your module depends on this it is regarded as an asynchronous module (i.e. you must call `$done` or the module will never finish loading). Example: ```JavaScript module.exports = function ($done) { $done(null, "finished loading"); }; ``` ```JavaScript container.register('f', function ($done) { $done(null, "success"); }); container.inject(function (f) { console.log(f); // prints "success" }); ``` ## Module annotations ### `$singleton` (boolean, default: true) ### `$factory` (boolean, default: true) ### `$dependencies` (array of strings) ## Events ### `initialized` ### `retrieved` ### `unhandled_error` ### `warning` ## Plugin Development ### `$modules` If your module exports a `$modules` object, the modules are registered in the container when you `use()` this package. ```JavaScript module.exports.$modules = { f: function (fs, path, $done) { fs.readFile('someFile.txt', $done); }, g: function (f) { return 'The text in someFile.txt is: ' + f; } }; ``` ### `$loaders` ### `$$..` ## License (MIT) Copyright (c) 2015 Julian Alexander Fleischer Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files (the "Software"), to deal in the Software without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so, subject to the following conditions: The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software. THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.