Autowire 2.2 (beta)

Angular-like automatic dependency injection for NodeJS.

Buzzwords: Easy to use, Rapid prototyping, Easy decoupling, Focus On Things That MatterTM

This module automagically autowires everything it can find. It finds installed modules (native node discovery) and user modules in current project folders. It also auto instantiates and injects class instances.

This is beta version: API may change with minor versions, performance may suffer.

Installation

npm install autowire

Usage

Autowire = require("autowire");

// inject modules which are auto discovered
Autowire(function(fs, express, MyLib) {

  // ... do stuff with autowired modules, without `require`ing them ...

  // MyLib.js location is auto discovered in project directory tree

  console.log(fs.existsSync("package.json"));

});

Advanced features

alias and wire

Autowire = require("autowire");

// Alias names. Here `lodash` will be requiered in place of `_`.
Autowire.alias("_", "lodash"); // this is an example, but _ is already automatically aliased

// Directly wire names to values, so `myVar` will be injected with `{"awesome": "dude!"}`
Autowire.wire("myVar", {"awesome": "dude!"});

Autowire(function(fs, express, _, myVar, DbModel) {

  // DbModel is auto discovered in project directory tree
  // and if it is not found error is thrown

  console.log(myVar); // {"awesome": "dude!"}
  console.log(_); // lodash object
  console.log(DbModel) // required ./module/DbModel.js

});

Autowire return value

In simplest terms

var x = Autowire(function(fs) { return fs; });

console.log(x === require('fs')); // true

So when we create new module we can easily export it with module.exports:

// ./lib/some/path/Test.js
module.exports = Autowire(function(fs, express, _, myVar) {

  // this will be attached to module.exports
  return {
    test: function(x) {
      console.log("x =", x);
    }
  };

});

// ./index.js
Autowire(function(Test) {
  Test.test(1337); // outputs to console: x = 1337
});

Class auto instantiation

You can mark a class for auto instantiation with automatic dependency injection.

Example

// ./lib/leet.js
module.exports = 1337;

// ./lib/MyClass.js
function MyClass(fs, leet) {
    this.fs = fs;
    this.leet = leet;
}

MyClass.autowire = {
  instantiate: true,
  
  // if set to true then class is instatiated only once for multiple injections
  singleton: false
};

module.exports = MyClass;

// ./index.js
Autowire = require("autowire");

Autowire(function(MyClass) {
    console.log(MyClass.fs.existsSync("index.js")); // true
    console.log(MyClass.leet); // 1337
});

Note: on each Autowire execution same class will be instantiated each time (cache won't work). If you want to have singleton behaviour set autowire.singleton to true on class object (e.g. MyClass.autowire = { instantiate: true, singleton: true };).

Autowire.getModuleByName(name)

Autowire can auto find a module by name. Just do var MyLib = Autowire.getModuleByName('MyLib');.

This is a syntactic sugar for var MyLib = Autowire(new Function("MyLib", "return MyLib;"));.

Autowire.include(path) i.e. include submodules of a module or include module at different path

// equivalent to require("urijs/src/URITemplate")
Autowire.include("urijs/src/URITemplate");

Autowire.include("/some/absolute/path/of/node-uuid");
Autowire.include("nodeUuid/some/sub/path/MyLib");

Autowire(function(URITemplate, nodeUuid, MyLib) {
  var uriTemplate = new URITemplate();
  var uuid = nodeUuid.v4();
});

Caching

Beside native NodeJS module cache Autowire caches paths and performes autodiscovery only once.

Why?

Imho this is just a better approach.

• You don't waste time on manually resolving module relative paths.
• You don't waste time on manually wiring dependencies.
• Module dependencies are clearly and well defined (no more finding all require invocations).
• You are forced to write code in a decoupled way (true dependency injection, without classes being instantiated inside constructors).
• Lexical-clojure encapsulation of modules makes more sense.
• You make your code DRYier (you write module name only once).
• Auto discovery is awesome!:D
• ???
• Profit!

Module auto discovery algorithm

Let's say we want to inject name.

Note: if name is an alias it will be first converted to aliased name, i.e. name = alias[name].

1. Find project root as the first folder up the directory structure with package.json. E.g. if we are at /a/b/c/d and there exists /a/b/package.json then /a/b is project root.
2. Map all file names to their absolute paths (ignore node_modules) and call it name_cache.
3. Try inner_cache[name] (hit Autowire inner cache)
4. Try to get path from name_cache[name] - if found then try to require(name_cache[name])
5. Try require(name)
6. If any try is successful: * If found module is a function with autowire.instantiate set to true
   • Instantiate as class instance
   • If autowire.singleton is true then put instance inside inner_cache: inner_cache[name] = instance
   • Return instance * Else
   • Save found module in inner_cache: inner_cache[name] = found_module
   • Return found module

TODO

• Auto discovery inside project folders (recursively) Done since version 2.2
• Auto instantiation of classes (configurable) Done since version 2.2
• Auto convert dash-case into camelCase, so e.g. we can with zero config inject node-uuid as nodeUuid. Done since version 2.2
• Somehow allow having same file names in different folders. Proposition: create namespaces as folders (and manually configurable namespaces). (Non?)-problem: variable names don't have / character.
• Write tests per module (e.g. tests for ModuleFinder)
• ECMAScript 6 support

License

The MIT License (MIT) Copyright (c) 2015 Jan Święcki

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.